Cytochromes P450 are a group of heme-thiolate monooxygenases. In liver microsomes, this enzyme is involved in an NADPH-dependent electron transport pathway. It oxidizes a variety of structurally unrelated compounds, including steroids, fatty acids, and xenobiotics.
The cytochrome P450 gene 4 family (CYP4) consists of a group of over 63 members that omega-hydroxylate the terminal carbon of fatty acids. In mammals, six subfamilies have been identified and three of these subfamily members show a preference in the metabolism of short (C7-C10)-CYP4B, medium (C10-C16)-CYP4A, and long (C16-C26)-CYP4F, saturated, unsaturated and branched chain fatty acids. These omega-hydroxylated fatty acids are converted to dicarboxylic acids, which are preferentially metabolized by the peroxisome beta-oxidation system to shorter chain fatty acids that are transported to the mitochondria for complete oxidation or used either to supply energy for peripheral tissues during starvation or in lipid synthesis. The differential regulation of the CYP4A and CYP4F genes during fasting, by peroxisome proliferators and in non-alcoholic fatty liver disease (NAFLD) suggests different roles in lipid metabolism. The omega-hydroxylation and inactivation of pro-inflammatory eicosanoids by members of the CYP4F subfamily and the association of the CYP4F2 and CYP4F3 genes with inflammatory celiac disease indicate an important role in the resolution of inflammation. Several human diseases have been genetically linked to the expression CYP4 gene polymorphic variants, which may link human susceptibility to diseases of lipid metabolism and the activation and resolution phases of inflammation. Understanding how the CYP4 genes are regulated during the fasting and feeding cycles and by endogenous lipids will provide therapeutic avenues in the treatment of metabolic disorders of lipid metabolism and inflammation.
Human cytochrome P450 4F2 (CYP4F2) catalyzes the ω-hydroxylation of the side chain of tocopherols (TOH) and tocotrienols (T3), the first step in their catabolism to polar metabolites excreted in urine. CYP4F2, in conjunction with α-TOH transfer protein, results in the conserved phenotype of selective retention of α-TOH. The purpose of this work was to determine the functional consequences of 2 common genetic variants in the human CYP4F2 gene on vitamin E-ω-hydroxylase specific activity using the 6 major dietary TOH and T3 as substrate. CYP4F2-mediated ω-hydroxylase specific activity was measured in microsomal preparations from insect cells that express wild-type or polymorphic variants of the human CYP4F2 protein. The W12G variant exhibited a greater enzyme specific activity (pmol product · min(-1) · pmol CYP4F2(-1)) compared with wild-type enzyme for both TOH and T3, 230-275% of wild-type toward α, γ, and δ-TOH and 350% of wild-type toward α, γ, and δ-T3. In contrast, the V433M variant had lower enzyme specific activity toward TOH (42-66% of wild type) but was without a significant effect on the metabolism of T3. Because CYP4F2 is the only enzyme currently shown to metabolize vitamin E in humans, the observed substrate-dependent alterations in enzyme activity associated with these genetic variants may result in alterations in vitamin E status in individuals carrying these mutations and constitute a source of variability in vitamin E status.
Human cytochrome P450 4F2 (CYP4F2) catalyzes the ω-hydroxylation of the side chain of tocopherols (TOH) and tocotrienols (T3), the first step in their catabolism to polar metabolites excreted in urine. CYP4F2, in conjunction with α-TOH transfer protein, results in the conserved phenotype of selective retention of α-TOH. The purpose of this work was to determine the functional consequences of 2 common genetic variants in the human CYP4F2 gene on vitamin E-ω-hydroxylase specific activity using the 6 major dietary TOH and T3 as substrate. CYP4F2-mediated ω-hydroxylase specific activity was measured in microsomal preparations from insect cells that express wild-type or polymorphic variants of the human CYP4F2 protein. The W12G variant exhibited a greater enzyme specific activity (pmol product · min(-1) · pmol CYP4F2(-1)) compared with wild-type enzyme for both TOH and T3, 230-275% of wild-type toward α, γ, and δ-TOH and 350% of wild-type toward α, γ, and δ-T3. In contrast, the V433M variant had lower enzyme specific activity toward TOH (42-66% of wild type) but was without a significant effect on the metabolism of T3. Because CYP4F2 is the only enzyme currently shown to metabolize vitamin E in humans, the observed substrate-dependent alterations in enzyme activity associated with these genetic variants may result in alterations in vitamin E status in individuals carrying these mutations and constitute a source of variability in vitamin E status.
J. Pharmacol. Exp. Ther. 285, 1327-1336 (1998)[PubMed:9618440]
20-Hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) is a principal arachidonic acid (AA) metabolite formed via P450-dependent oxidation in hepatic and renal microsomes. Although 20-HETE plays an important role in the regulation of cell and/or organ physiology, the P450 enzyme(s) catalyzing its formation in humans remain undefined. In this study, we have characterized AA omega-hydroxylation to 20-HETE by human hepatic microsomes and identified the underlying P450s. Analysis of microsomal AA omega-hydroxylation revealed biphasic kinetics (KM1 and VMAX1 = 23 microM and 5.5 min-1; KM2 and VMAX2 = 144 microM and 18.8 min-1) consistent with catalysis by at least two enzymes. Of the human P450s examined, CYP4A11 and CYP4F2 were both potent AA omega-hydroxylases, exhibiting rates of 15.6 and 6.8 nmol 20-HETE formed/min/nmol P450, respectively. Kinetic parameters of 20-HETE formation by CYP4F2 (KM = 24 microM; VMAX = 7.4 min-1) and CYP4A11 (KM = 228 microM; VMAX = 49.1 min-1) resembled the low and high KM components, respectively, found in liver microsomes. Antibodies to CYP4F2 markedly inhibited (93.4 +/- 6%; n = 5) formation of 20-HETE by hepatic microsomes, whereas antibodies to CYP4A11 were much less inhibitory (13.0 +/- 9%; n = 5). Moreover, a strong correlation (r = 0.78; P < .02) was found between microsomal CYP4F2 content and AA omega-hydroxylation among nine subjects. The correlation (r = 0.76; P < .02) also noted between CYP4A11 content and 20-HETE formation stemmed from the relationship (r = 0.83; P < . 02) between hepatic CYP4A11 and CYP4F2 levels in the subjects. Finally, immunoblot analysis revealed that in addition to liver, both P450s also were expressed in human kidney. Our results indicate that AA omega-hydroxylation in human liver is catalyzed by two enzymes of the CYP4 gene family, namely CYP4F2 and CYP4A11, and that CYP4F2 underlies most 20-HETE formation occurring at relevant AA concentrations.
Catalysis of the reaction: arachidonic acid + O2 + NADPH + H+ = 20-HETE + NADP+ + H2O. Arachidonic acid is also known as (5Z,8Z,11Z,14Z)-icosatetraenoic acid, and 20-HETE is also known as (5Z,8Z,11Z,14Z)-20-hydroxyicosa-5,8,11,14-tetraenoic acid.
J. Pharmacol. Exp. Ther. 285, 1327-1336 (1998)[PubMed:9618440]
20-Hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) is a principal arachidonic acid (AA) metabolite formed via P450-dependent oxidation in hepatic and renal microsomes. Although 20-HETE plays an important role in the regulation of cell and/or organ physiology, the P450 enzyme(s) catalyzing its formation in humans remain undefined. In this study, we have characterized AA omega-hydroxylation to 20-HETE by human hepatic microsomes and identified the underlying P450s. Analysis of microsomal AA omega-hydroxylation revealed biphasic kinetics (KM1 and VMAX1 = 23 microM and 5.5 min-1; KM2 and VMAX2 = 144 microM and 18.8 min-1) consistent with catalysis by at least two enzymes. Of the human P450s examined, CYP4A11 and CYP4F2 were both potent AA omega-hydroxylases, exhibiting rates of 15.6 and 6.8 nmol 20-HETE formed/min/nmol P450, respectively. Kinetic parameters of 20-HETE formation by CYP4F2 (KM = 24 microM; VMAX = 7.4 min-1) and CYP4A11 (KM = 228 microM; VMAX = 49.1 min-1) resembled the low and high KM components, respectively, found in liver microsomes. Antibodies to CYP4F2 markedly inhibited (93.4 +/- 6%; n = 5) formation of 20-HETE by hepatic microsomes, whereas antibodies to CYP4A11 were much less inhibitory (13.0 +/- 9%; n = 5). Moreover, a strong correlation (r = 0.78; P < .02) was found between microsomal CYP4F2 content and AA omega-hydroxylation among nine subjects. The correlation (r = 0.76; P < .02) also noted between CYP4A11 content and 20-HETE formation stemmed from the relationship (r = 0.83; P < . 02) between hepatic CYP4A11 and CYP4F2 levels in the subjects. Finally, immunoblot analysis revealed that in addition to liver, both P450s also were expressed in human kidney. Our results indicate that AA omega-hydroxylation in human liver is catalyzed by two enzymes of the CYP4 gene family, namely CYP4F2 and CYP4A11, and that CYP4F2 underlies most 20-HETE formation occurring at relevant AA concentrations.
J. Biol. Chem. 275, 4118-4126 (2000)[PubMed:10660572]
20-hydroxyeicosatetraenoic acid (20-HETE), an omega-hydroxylated arachidonic acid (AA) metabolite, elicits specific effects on kidney vascular and tubular function that, in turn, influence blood pressure control. The human kidney's capacity to convert AA to 20-HETE is unclear, however, as is the underlying P450 catalyst. Microsomes from human kidney cortex were found to convert AA to a single major product, namely 20-HETE, but failed to catalyze AA epoxygenation and midchain hydroxylation. Despite the monophasic nature of renal AA omega-hydroxylation kinetics, immunochemical studies revealed participation of two P450s, CYP4F2 and CYP4A11, since antibodies to these enzymes inhibited 20-HETE formation by 65. 9 +/- 17 and 32.5 +/- 14%, respectively. Western blotting confirmed abundant expression of these CYP4 proteins in human kidney and revealed that other AA-oxidizing P450s, including CYP2C8, CYP2C9, and CYP2E1, were not expressed. Immunocytochemistry showed CYP4F2 and CYP4A11 expression in only the S2 and S3 segments of proximal tubules in cortex and outer medulla. Our results demonstrate that CYP4F2 and CYP4A11 underlie conversion of AA to 20-HETE, a natriuretic and vasoactive eicosanoid, in human kidney. Considering their proximal tubular localization, these P450 enzymes may partake in pivotal renal functions, including the regulation of salt and water balance, and arterial blood pressure itself.
Leukotriene B4 (LTB4), an arachidonic acid derivative, is a potent proinflammatory agent whose actions are terminated by catabolism via a microsomal omega-hydroxylation pathway. Although the liver serves as the principal site for LTB4 clearance from the systemic circulation, the attributes of hepatic LTB4 metabolism are ill defined in humans. Thus, we examined metabolism of LTB4 to its omega-hydroxylated metabolite 20-hydroxyleukotriene B4 (20-OH LTB4) by human liver microsomes and also purified the hepatic P450 enzyme underlying this reaction. Liver microsomes from 10 different subjects converted LTB4 to 20-OH LTB4 at similar rates (1.06 +/- 0.3 nmol/min/nmol P450; 0.25 +/- 0.1 nmol/min/mg protein). Analysis of the microsomal LTB4 20-hydroxylation reaction revealed kinetic parameters (apparent Km of 74.8 microM with a VMAX of 2.42 nmol/min/nmol P450) consistent with catalysis by a single P450 enzyme. Conventional chromatography combined with immunochemical screening with rat CYP4A1 antibodies was then used to isolate a P450 enzyme from human liver microsomes with a molecular weight of 57,000 and an NH2-terminal amino acid sequence 94% homologous (12Trp --> 12Gly) over the first 17 residues with the human CYP4F2 cDNA-derived sequence. Upon reconstitution with P450 reductase and phospholipid, CYP4F2 converted LTB4 to 20-OH LTB4 at a turnover rate of 392 pmol/min/nmol P450, whereas the other human liver P450s tested, including CYP4A11, exhibited neglible LTB4 omega-hydroxylase activity. Polyclonal antibodies to CYP4F2 were found to markedly inhibit (91.9 +/- 5%; n = 5) LTB4 20-hydroxylation by human liver microsomes. Microsomal 20-OH LTB4 formation was also inhibited 30% by arachidonic acid, a known CYP4F2 substrate, and 50% by prostaglandin A1 but was unaffected by lauric acid, palmitic acid, and PGF2alpha. Finally, a strong correlation (r = 0.86; P < 0.002; n = 10) was observed between CYP4F2 content and LTB4 20-hydroxylase activity in the human liver samples. Our results indicate that CYP4F2 is the principle LTB4 omega-hydroxylating enzyme expressed in human liver and, as such, may play an important role in regulating circulating as well as hepatic levels of this powerful proinflammatory eicosanoid.
We have isolated and sequenced a cDNA for human liver LTB4 omega-hydroxylase. The cDNA encoded a protein of 520 amino acids with a molecular weight of 59,853 Da. The cDNA-deduced amino acid sequence showed 87.3% homology to that of human polymorphonuclear leukocytes (PMN) LTB4 omega-hydroxylase (CYP4F3). Northern blot analysis revealed that the mRNA hybridized to the specific cDNA fragment is expressed in human liver, but not in human PMN. The microsomes from yeast cells transfected with the cDNA catalyzed the omega-hydroxylation of LTB4 with a Km of 44.8 microM. These results clearly show that a new form of the CYP4F LTB4 omega-hydroxylase exists in human liver.
Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionIntAct
Systematic identification of direct protein-protein interactions is often hampered by difficulties in expressing and purifying the corresponding full-length proteins. By taking advantage of the modular nature of many regulatory proteins, we attempted to simplify protein-protein interactions to the corresponding domain-ligand recognition and employed peptide arrays to identify such binding events. A group of 12 Src homology (SH) 3 domains from eight human proteins (Swiss-Prot ID: SRC, PLCG1, P85A, NCK1, GRB2, FYN, CRK) were used to screen a peptide target array composed of 1536 potential ligands, which led to the identification of 921 binary interactions between these proteins and 284 targets. To assess the efficiency of the peptide array target screening (PATS) method in identifying authentic protein-protein interactions, we examined a set of interactions mediated by the PLCgamma1 SH3 domain by coimmunoprecipitation and/or affinity pull-downs using full-length proteins and achieved a 75% success rate. Furthermore, we characterized a novel interaction between PLCgamma1 and hematopoietic progenitor kinase 1 (HPK1) identified by PATS and demonstrated that the PLCgamma1 SH3 domain negatively regulated HPK1 kinase activity. Compared to protein interactions listed in the online predicted human interaction protein database (OPHID), the majority of interactions identified by PATS are novel, suggesting that, when extended to the large number of peptide interaction domains encoded by the human genome, PATS should aid in the mapping of the human interactome.
Human cytochrome P450 4F2 (CYP4F2) catalyzes the ω-hydroxylation of the side chain of tocopherols (TOH) and tocotrienols (T3), the first step in their catabolism to polar metabolites excreted in urine. CYP4F2, in conjunction with α-TOH transfer protein, results in the conserved phenotype of selective retention of α-TOH. The purpose of this work was to determine the functional consequences of 2 common genetic variants in the human CYP4F2 gene on vitamin E-ω-hydroxylase specific activity using the 6 major dietary TOH and T3 as substrate. CYP4F2-mediated ω-hydroxylase specific activity was measured in microsomal preparations from insect cells that express wild-type or polymorphic variants of the human CYP4F2 protein. The W12G variant exhibited a greater enzyme specific activity (pmol product · min(-1) · pmol CYP4F2(-1)) compared with wild-type enzyme for both TOH and T3, 230-275% of wild-type toward α, γ, and δ-TOH and 350% of wild-type toward α, γ, and δ-T3. In contrast, the V433M variant had lower enzyme specific activity toward TOH (42-66% of wild type) but was without a significant effect on the metabolism of T3. Because CYP4F2 is the only enzyme currently shown to metabolize vitamin E in humans, the observed substrate-dependent alterations in enzyme activity associated with these genetic variants may result in alterations in vitamin E status in individuals carrying these mutations and constitute a source of variability in vitamin E status.
Neural prostheses aim to provide treatment options for individuals with nervous-system disease or injury. It is necessary, however, to increase the performance of such systems before they can be clinically viable for patients with motor dysfunction. One performance limitation is the presence of correlated trial-to-trial variability that can cause neural responses to wax and wane in concert as the subject is, for example, more attentive or more fatigued. If a system does not properly account for this variability, it may mistakenly interpret such variability as an entirely different intention by the subject. We report here the design and characterization of factor-analysis (FA)-based decoding algorithms that can contend with this confound. We characterize the decoders (classifiers) on experimental data where monkeys performed both a real reach task and a prosthetic cursor task while we recorded from 96 electrodes implanted in dorsal premotor cortex. The decoder attempts to infer the underlying factors that comodulate the neurons' responses and can use this information to substantially lower error rates (one of eight reach endpoint predictions) by <or=75% (e.g., approximately 20% total prediction error using traditional independent Poisson models reduced to approximately 5%). We also examine additional key aspects of these new algorithms: the effect of neural integration window length on performance, an extension of the algorithms to use Poisson statistics, and the effect of training set size on the decoding accuracy of test data. We found that FA-based methods are most effective for integration windows >150 ms, although still advantageous at shorter timescales, that Gaussian-based algorithms performed better than the analogous Poisson-based algorithms and that the FA algorithm is robust even with a limited amount of training data. We propose that FA-based methods are effective in modeling correlated trial-to-trial neural variability and can be used to substantially increase overall prosthetic system performance.
The chemical reactions and pathways involving arachidonic acid, a straight chain fatty acid with 20 carbon atoms and four double bonds per molecule. Arachidonic acid is the all-Z-(5,8,11,14)-isomer.
J. Biol. Chem. 275, 4118-4126 (2000)[PubMed:10660572]
20-hydroxyeicosatetraenoic acid (20-HETE), an omega-hydroxylated arachidonic acid (AA) metabolite, elicits specific effects on kidney vascular and tubular function that, in turn, influence blood pressure control. The human kidney's capacity to convert AA to 20-HETE is unclear, however, as is the underlying P450 catalyst. Microsomes from human kidney cortex were found to convert AA to a single major product, namely 20-HETE, but failed to catalyze AA epoxygenation and midchain hydroxylation. Despite the monophasic nature of renal AA omega-hydroxylation kinetics, immunochemical studies revealed participation of two P450s, CYP4F2 and CYP4A11, since antibodies to these enzymes inhibited 20-HETE formation by 65. 9 +/- 17 and 32.5 +/- 14%, respectively. Western blotting confirmed abundant expression of these CYP4 proteins in human kidney and revealed that other AA-oxidizing P450s, including CYP2C8, CYP2C9, and CYP2E1, were not expressed. Immunocytochemistry showed CYP4F2 and CYP4A11 expression in only the S2 and S3 segments of proximal tubules in cortex and outer medulla. Our results demonstrate that CYP4F2 and CYP4A11 underlie conversion of AA to 20-HETE, a natriuretic and vasoactive eicosanoid, in human kidney. Considering their proximal tubular localization, these P450 enzymes may partake in pivotal renal functions, including the regulation of salt and water balance, and arterial blood pressure itself.
The chemical reactions and pathways involving a drug, a substance used in the diagnosis, treatment or prevention of a disease; as used here antibiotic substances (see antibiotic metabolism) are considered to be drugs, even if not used in medical or veterinary practice.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
Drug Metab. Pharmacokinet. 26, 130-136 (2011)[PubMed:21084764]
Warfarin exhibits wide interpatient variability in dosing requirements. Recent studies have shown a novel polymorphism (rs2108622, V433M) in the CYP4F2 gene to be associated with variability in warfarin requirements in Caucasians. The purpose of this study was to evaluate the impact of rs2108622 on warfarin dose requirements in the Asian population. The mean warfarin dose was found to be significantly lower in patients carrying homozygous wild-type allele CC when compared with patients carrying variant alleles CT and TT (CC vs CT+TT: 3.0 mg/day vs 3.75 mg/day, p = 0.033). In patients harboring VKORC1 diplotypes associated with low warfarin requirements, a linear regression model which included age, weight, CYP2C9 and CYP4F2 variants accounted for 38% of the variability in warfarin dose. Approximately 11% of the dose variation was explained by CYP4F2 rs2108622 (p = 0.004). The influence of rs2108622 in patients harboring VKORC1 diplotypes associated with high warfarin requirements was not significant. This study suggests that CYP4F2 rs2108622 may significantly affect warfarin dose requirements in carriers of VKORC1 low-dose-associated diplotypes.
Evidence
2:
Inferred from Mutant PhenotypeUniProtKB
The aim of this study was to investigate whether the VKORC1*3 (rs7294/9041 G > A), VKORC1*4 (rs17708472/6009 C > T), and CYP4F2 (rs2108622/1347 C > T) polymorphisms were associated with elevated warfarin maintenance dose requirements in patients with myocardial infarction (n = 105) from the Warfarin Aspirin Reinfarction Study (WARIS-II). We found significant associations between elevated warfarin dose requirements and VKORC1*3 and VKORC1*4 polymorphisms (P = .001 and P = .004, resp.), whereas CYP4F2 (1347 C > T) showed a weak association on higher warfarin dose requirements (P = .09). However, analysing these variant alleles in a regression analysis together with our previously reported data on VKORC1*2, CYP2C9*2 and CYP2C9*3 polymorphisms, gave no significant associations for neither VKORC1*3, VKORC1*4 nor CYP4F2 (1347 C > T). In conclusion, in patients with myocardial infarction, the individual contribution to warfarin dose requirements from VKORC1*3, VKORC1*4, and CYP4F2 (1347 C > T) polymorphisms was negligible. Our results indicate that pharmacogenetic testing for VKORC1*2, CYP2C9*2 and CYP2C9*3 is more informative regarding warfarin dose requirements than testing for VKORC1*3, VKORC1*4, and CYP4F2 (1347 C > T) polymorphisms.
The chemical reactions and pathways by which arachidonic acid is converted to other compounds including epoxyeicosatrienoic acids and dihydroxyeicosatrienoic acids.
Human cytochrome P450 4F2 (CYP4F2) catalyzes the ω-hydroxylation of the side chain of tocopherols (TOH) and tocotrienols (T3), the first step in their catabolism to polar metabolites excreted in urine. CYP4F2, in conjunction with α-TOH transfer protein, results in the conserved phenotype of selective retention of α-TOH. The purpose of this work was to determine the functional consequences of 2 common genetic variants in the human CYP4F2 gene on vitamin E-ω-hydroxylase specific activity using the 6 major dietary TOH and T3 as substrate. CYP4F2-mediated ω-hydroxylase specific activity was measured in microsomal preparations from insect cells that express wild-type or polymorphic variants of the human CYP4F2 protein. The W12G variant exhibited a greater enzyme specific activity (pmol product · min(-1) · pmol CYP4F2(-1)) compared with wild-type enzyme for both TOH and T3, 230-275% of wild-type toward α, γ, and δ-TOH and 350% of wild-type toward α, γ, and δ-T3. In contrast, the V433M variant had lower enzyme specific activity toward TOH (42-66% of wild type) but was without a significant effect on the metabolism of T3. Because CYP4F2 is the only enzyme currently shown to metabolize vitamin E in humans, the observed substrate-dependent alterations in enzyme activity associated with these genetic variants may result in alterations in vitamin E status in individuals carrying these mutations and constitute a source of variability in vitamin E status.
J. Pharmacol. Exp. Ther. 285, 1327-1336 (1998)[PubMed:9618440]
20-Hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) is a principal arachidonic acid (AA) metabolite formed via P450-dependent oxidation in hepatic and renal microsomes. Although 20-HETE plays an important role in the regulation of cell and/or organ physiology, the P450 enzyme(s) catalyzing its formation in humans remain undefined. In this study, we have characterized AA omega-hydroxylation to 20-HETE by human hepatic microsomes and identified the underlying P450s. Analysis of microsomal AA omega-hydroxylation revealed biphasic kinetics (KM1 and VMAX1 = 23 microM and 5.5 min-1; KM2 and VMAX2 = 144 microM and 18.8 min-1) consistent with catalysis by at least two enzymes. Of the human P450s examined, CYP4A11 and CYP4F2 were both potent AA omega-hydroxylases, exhibiting rates of 15.6 and 6.8 nmol 20-HETE formed/min/nmol P450, respectively. Kinetic parameters of 20-HETE formation by CYP4F2 (KM = 24 microM; VMAX = 7.4 min-1) and CYP4A11 (KM = 228 microM; VMAX = 49.1 min-1) resembled the low and high KM components, respectively, found in liver microsomes. Antibodies to CYP4F2 markedly inhibited (93.4 +/- 6%; n = 5) formation of 20-HETE by hepatic microsomes, whereas antibodies to CYP4A11 were much less inhibitory (13.0 +/- 9%; n = 5). Moreover, a strong correlation (r = 0.78; P < .02) was found between microsomal CYP4F2 content and AA omega-hydroxylation among nine subjects. The correlation (r = 0.76; P < .02) also noted between CYP4A11 content and 20-HETE formation stemmed from the relationship (r = 0.83; P < . 02) between hepatic CYP4A11 and CYP4F2 levels in the subjects. Finally, immunoblot analysis revealed that in addition to liver, both P450s also were expressed in human kidney. Our results indicate that AA omega-hydroxylation in human liver is catalyzed by two enzymes of the CYP4 gene family, namely CYP4F2 and CYP4A11, and that CYP4F2 underlies most 20-HETE formation occurring at relevant AA concentrations.
The chemical reactions and pathways resulting in the breakdown of leukotriene B4, a leukotriene composed of (6Z,8E,10E,14Z)-eicosatetraenoic acid having (5S)- and (12R)-hydroxy substituents.
Leukotriene B4 (LTB4), an arachidonic acid derivative, is a potent proinflammatory agent whose actions are terminated by catabolism via a microsomal omega-hydroxylation pathway. Although the liver serves as the principal site for LTB4 clearance from the systemic circulation, the attributes of hepatic LTB4 metabolism are ill defined in humans. Thus, we examined metabolism of LTB4 to its omega-hydroxylated metabolite 20-hydroxyleukotriene B4 (20-OH LTB4) by human liver microsomes and also purified the hepatic P450 enzyme underlying this reaction. Liver microsomes from 10 different subjects converted LTB4 to 20-OH LTB4 at similar rates (1.06 +/- 0.3 nmol/min/nmol P450; 0.25 +/- 0.1 nmol/min/mg protein). Analysis of the microsomal LTB4 20-hydroxylation reaction revealed kinetic parameters (apparent Km of 74.8 microM with a VMAX of 2.42 nmol/min/nmol P450) consistent with catalysis by a single P450 enzyme. Conventional chromatography combined with immunochemical screening with rat CYP4A1 antibodies was then used to isolate a P450 enzyme from human liver microsomes with a molecular weight of 57,000 and an NH2-terminal amino acid sequence 94% homologous (12Trp --> 12Gly) over the first 17 residues with the human CYP4F2 cDNA-derived sequence. Upon reconstitution with P450 reductase and phospholipid, CYP4F2 converted LTB4 to 20-OH LTB4 at a turnover rate of 392 pmol/min/nmol P450, whereas the other human liver P450s tested, including CYP4A11, exhibited neglible LTB4 omega-hydroxylase activity. Polyclonal antibodies to CYP4F2 were found to markedly inhibit (91.9 +/- 5%; n = 5) LTB4 20-hydroxylation by human liver microsomes. Microsomal 20-OH LTB4 formation was also inhibited 30% by arachidonic acid, a known CYP4F2 substrate, and 50% by prostaglandin A1 but was unaffected by lauric acid, palmitic acid, and PGF2alpha. Finally, a strong correlation (r = 0.86; P < 0.002; n = 10) was observed between CYP4F2 content and LTB4 20-hydroxylase activity in the human liver samples. Our results indicate that CYP4F2 is the principle LTB4 omega-hydroxylating enzyme expressed in human liver and, as such, may play an important role in regulating circulating as well as hepatic levels of this powerful proinflammatory eicosanoid.
Human liver leukotriene B4 (LTB4) omega-hydroxylase (CYP4F2) plays an important role in the metabolic inactivation and degradation of LTB4, a potent mediator of inflammation. The regulatory mechanism for the transcription of CYP4F2 has not yet been clarified. Here, we report that CYP4F2 is constitutively expressed in a human hepatoma cell line, HepG2, and is not induced by clofibrate. We isolated the gene encoding CYP4F2 and determined its genomic organization and the functional activity of its promoters. The CYP4F2 gene contains at least 13 exons with its open reading frame being encoded from exon II to exon XIII. Exon I includes 49 bp of a 5' untranslated sequence. The structure of this gene is very similar to that of the CYP4F3 gene earlier reported by Kikuta et al. (DNA Cell Biol 1998;17:221-230). The 5' flanking sequence downstream from -165 of the CYP4F2 gene has 75% similarity to the corresponding region of the CYP4F3 gene. However, common putative regulating elements in the two human CYP4F genes were not detected except for the TATA box. The elements recognized by nuclear receptors were not observed within its 5' flanking region. Deletion of the 5' flanking regions containing putative regulating elements recognized by HNF-3beta, CDP CR, and p300 caused alterations in the transcriptional activity. The region from -83 to -67 was necessary for transcription, but the TATA sequence was not. Our results indicate that the human two CYP4F genes evolved by duplication and alterations of the transcription regulation region and the site of exon III.
We have isolated and sequenced a cDNA for human liver LTB4 omega-hydroxylase. The cDNA encoded a protein of 520 amino acids with a molecular weight of 59,853 Da. The cDNA-deduced amino acid sequence showed 87.3% homology to that of human polymorphonuclear leukocytes (PMN) LTB4 omega-hydroxylase (CYP4F3). Northern blot analysis revealed that the mRNA hybridized to the specific cDNA fragment is expressed in human liver, but not in human PMN. The microsomes from yeast cells transfected with the cDNA catalyzed the omega-hydroxylation of LTB4 with a Km of 44.8 microM. These results clearly show that a new form of the CYP4F LTB4 omega-hydroxylase exists in human liver.
The cytochrome P450 gene 4 family (CYP4) consists of a group of over 63 members that omega-hydroxylate the terminal carbon of fatty acids. In mammals, six subfamilies have been identified and three of these subfamily members show a preference in the metabolism of short (C7-C10)-CYP4B, medium (C10-C16)-CYP4A, and long (C16-C26)-CYP4F, saturated, unsaturated and branched chain fatty acids. These omega-hydroxylated fatty acids are converted to dicarboxylic acids, which are preferentially metabolized by the peroxisome beta-oxidation system to shorter chain fatty acids that are transported to the mitochondria for complete oxidation or used either to supply energy for peripheral tissues during starvation or in lipid synthesis. The differential regulation of the CYP4A and CYP4F genes during fasting, by peroxisome proliferators and in non-alcoholic fatty liver disease (NAFLD) suggests different roles in lipid metabolism. The omega-hydroxylation and inactivation of pro-inflammatory eicosanoids by members of the CYP4F subfamily and the association of the CYP4F2 and CYP4F3 genes with inflammatory celiac disease indicate an important role in the resolution of inflammation. Several human diseases have been genetically linked to the expression CYP4 gene polymorphic variants, which may link human susceptibility to diseases of lipid metabolism and the activation and resolution phases of inflammation. Understanding how the CYP4 genes are regulated during the fasting and feeding cycles and by endogenous lipids will provide therapeutic avenues in the treatment of metabolic disorders of lipid metabolism and inflammation.
Neural prostheses aim to provide treatment options for individuals with nervous-system disease or injury. It is necessary, however, to increase the performance of such systems before they can be clinically viable for patients with motor dysfunction. One performance limitation is the presence of correlated trial-to-trial variability that can cause neural responses to wax and wane in concert as the subject is, for example, more attentive or more fatigued. If a system does not properly account for this variability, it may mistakenly interpret such variability as an entirely different intention by the subject. We report here the design and characterization of factor-analysis (FA)-based decoding algorithms that can contend with this confound. We characterize the decoders (classifiers) on experimental data where monkeys performed both a real reach task and a prosthetic cursor task while we recorded from 96 electrodes implanted in dorsal premotor cortex. The decoder attempts to infer the underlying factors that comodulate the neurons' responses and can use this information to substantially lower error rates (one of eight reach endpoint predictions) by <or=75% (e.g., approximately 20% total prediction error using traditional independent Poisson models reduced to approximately 5%). We also examine additional key aspects of these new algorithms: the effect of neural integration window length on performance, an extension of the algorithms to use Poisson statistics, and the effect of training set size on the decoding accuracy of test data. We found that FA-based methods are most effective for integration windows >150 ms, although still advantageous at shorter timescales, that Gaussian-based algorithms performed better than the analogous Poisson-based algorithms and that the FA algorithm is robust even with a limited amount of training data. We propose that FA-based methods are effective in modeling correlated trial-to-trial neural variability and can be used to substantially increase overall prosthetic system performance.
Arachidonic acid is a major fatty acid that can be metabolized by the cytochrome P450 enzyme to a number of bioactive eicosanoids. A major metabolite of this oxidation is 20-hydroxyeicosatetraenoic acid, which acts as a potent vasoconstrictor. However, in the kidney, its vasoconstrictor actions can be offset by its natriuretic properties. A guanine-to-adenine polymorphism in the CYP4F2 gene was associated with a reduction in 20-hydroxyeicosatetraenoic acid production in vitro. A thymidine-to-cytosine polymorphism in the CYP4A11 gene reduced catalytic activity by >50% in vitro and was associated with hypertension. The aim was to determine whether these 2 mutations are associated with urinary 20-hydroxyeicosatetraenoic acid excretion and blood pressure in humans. For the CYP4F2, 51% were homozygous for the G allele, 40% were carriers, and 9% were homozygous for the A allele. For CYP4A11, 72% were homozygous for the T allele, 25% were carriers, and 3% were homozygous for the C allele. The CYP4F2 GA/AA genotype was significantly associated with an increase in both 20-hydroxyeicosatetraenoic acid excretion and systolic blood pressure. The CYP4A11 CC/TC genotype was significantly associated with a reduction in 20-hydroxyeicosatetraenoic acid excretion but was not associated with blood pressure. We have demonstrated for the first time in humans that polymorphisms of the CYP4F2 and CYP4A11 genes have opposite effects on 20-hydroxyeicosatetraenoic acid excretion. The positive association between the CYP4F2 GA/AA genotype and both systolic blood pressure and 20-hydroxyeicosatetraenoic acid excretion strengthens a role for 20-hydroxyeicosatetraenoic acid in the modulation of blood pressure.
A metabolic process that results in the removal or addition of one or more electrons to or from a substance, with or without the concomitant removal or addition of a proton or protons.
J. Pharmacol. Exp. Ther. 285, 1327-1336 (1998)[PubMed:9618440]
20-Hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) is a principal arachidonic acid (AA) metabolite formed via P450-dependent oxidation in hepatic and renal microsomes. Although 20-HETE plays an important role in the regulation of cell and/or organ physiology, the P450 enzyme(s) catalyzing its formation in humans remain undefined. In this study, we have characterized AA omega-hydroxylation to 20-HETE by human hepatic microsomes and identified the underlying P450s. Analysis of microsomal AA omega-hydroxylation revealed biphasic kinetics (KM1 and VMAX1 = 23 microM and 5.5 min-1; KM2 and VMAX2 = 144 microM and 18.8 min-1) consistent with catalysis by at least two enzymes. Of the human P450s examined, CYP4A11 and CYP4F2 were both potent AA omega-hydroxylases, exhibiting rates of 15.6 and 6.8 nmol 20-HETE formed/min/nmol P450, respectively. Kinetic parameters of 20-HETE formation by CYP4F2 (KM = 24 microM; VMAX = 7.4 min-1) and CYP4A11 (KM = 228 microM; VMAX = 49.1 min-1) resembled the low and high KM components, respectively, found in liver microsomes. Antibodies to CYP4F2 markedly inhibited (93.4 +/- 6%; n = 5) formation of 20-HETE by hepatic microsomes, whereas antibodies to CYP4A11 were much less inhibitory (13.0 +/- 9%; n = 5). Moreover, a strong correlation (r = 0.78; P < .02) was found between microsomal CYP4F2 content and AA omega-hydroxylation among nine subjects. The correlation (r = 0.76; P < .02) also noted between CYP4A11 content and 20-HETE formation stemmed from the relationship (r = 0.83; P < . 02) between hepatic CYP4A11 and CYP4F2 levels in the subjects. Finally, immunoblot analysis revealed that in addition to liver, both P450s also were expressed in human kidney. Our results indicate that AA omega-hydroxylation in human liver is catalyzed by two enzymes of the CYP4 gene family, namely CYP4F2 and CYP4A11, and that CYP4F2 underlies most 20-HETE formation occurring at relevant AA concentrations.
Human cytochrome P450 4F2 (CYP4F2) catalyzes the ω-hydroxylation of the side chain of tocopherols (TOH) and tocotrienols (T3), the first step in their catabolism to polar metabolites excreted in urine. CYP4F2, in conjunction with α-TOH transfer protein, results in the conserved phenotype of selective retention of α-TOH. The purpose of this work was to determine the functional consequences of 2 common genetic variants in the human CYP4F2 gene on vitamin E-ω-hydroxylase specific activity using the 6 major dietary TOH and T3 as substrate. CYP4F2-mediated ω-hydroxylase specific activity was measured in microsomal preparations from insect cells that express wild-type or polymorphic variants of the human CYP4F2 protein. The W12G variant exhibited a greater enzyme specific activity (pmol product · min(-1) · pmol CYP4F2(-1)) compared with wild-type enzyme for both TOH and T3, 230-275% of wild-type toward α, γ, and δ-TOH and 350% of wild-type toward α, γ, and δ-T3. In contrast, the V433M variant had lower enzyme specific activity toward TOH (42-66% of wild type) but was without a significant effect on the metabolism of T3. Because CYP4F2 is the only enzyme currently shown to metabolize vitamin E in humans, the observed substrate-dependent alterations in enzyme activity associated with these genetic variants may result in alterations in vitamin E status in individuals carrying these mutations and constitute a source of variability in vitamin E status.
Leukotriene B4 (LTB4), an arachidonic acid derivative, is a potent proinflammatory agent whose actions are terminated by catabolism via a microsomal omega-hydroxylation pathway. Although the liver serves as the principal site for LTB4 clearance from the systemic circulation, the attributes of hepatic LTB4 metabolism are ill defined in humans. Thus, we examined metabolism of LTB4 to its omega-hydroxylated metabolite 20-hydroxyleukotriene B4 (20-OH LTB4) by human liver microsomes and also purified the hepatic P450 enzyme underlying this reaction. Liver microsomes from 10 different subjects converted LTB4 to 20-OH LTB4 at similar rates (1.06 +/- 0.3 nmol/min/nmol P450; 0.25 +/- 0.1 nmol/min/mg protein). Analysis of the microsomal LTB4 20-hydroxylation reaction revealed kinetic parameters (apparent Km of 74.8 microM with a VMAX of 2.42 nmol/min/nmol P450) consistent with catalysis by a single P450 enzyme. Conventional chromatography combined with immunochemical screening with rat CYP4A1 antibodies was then used to isolate a P450 enzyme from human liver microsomes with a molecular weight of 57,000 and an NH2-terminal amino acid sequence 94% homologous (12Trp --> 12Gly) over the first 17 residues with the human CYP4F2 cDNA-derived sequence. Upon reconstitution with P450 reductase and phospholipid, CYP4F2 converted LTB4 to 20-OH LTB4 at a turnover rate of 392 pmol/min/nmol P450, whereas the other human liver P450s tested, including CYP4A11, exhibited neglible LTB4 omega-hydroxylase activity. Polyclonal antibodies to CYP4F2 were found to markedly inhibit (91.9 +/- 5%; n = 5) LTB4 20-hydroxylation by human liver microsomes. Microsomal 20-OH LTB4 formation was also inhibited 30% by arachidonic acid, a known CYP4F2 substrate, and 50% by prostaglandin A1 but was unaffected by lauric acid, palmitic acid, and PGF2alpha. Finally, a strong correlation (r = 0.86; P < 0.002; n = 10) was observed between CYP4F2 content and LTB4 20-hydroxylase activity in the human liver samples. Our results indicate that CYP4F2 is the principle LTB4 omega-hydroxylating enzyme expressed in human liver and, as such, may play an important role in regulating circulating as well as hepatic levels of this powerful proinflammatory eicosanoid.
20-Hydroxyeicosatetraenoic acid (20-HETE) plays an important role in the regulation of renal tubular and vascular function and a deficiency in the renal formation of 20-HETE has been linked to the development of hypertension. The cytochrome P450 4F2 (CYP4F2) gene encodes for the major CYP enzyme responsible for the synthesis of 20-HETE in the human kidney. We screened two human sampling panels (African and European Americans: n = 24 and 23 individuals, respectively) using PCR and DNA resequencing to identify informative SNPs in the coding region of the CYP4F2 gene. Two nonsynonymous SNPs that lead to amino acid changes at position 12 (W12G) and 433 (V433M), were identified. Both of these variants were found to be frequent in both African and European American sampling panels (9-21% minor allele frequency), and the W12G polymorphism exhibited extensive linkage disequilibrium with surrounding SNPs. To determine the functional significance of these mutations on the ability of the CYP4F2 enzyme to metabolize arachidonic acid and leukotriene B(4) (LTB(4)), recombinant baculoviruses containing four different human CYP4F2 variants (i.e., W12/V433, W12/M433, G12/V433, G12/M433) were generated and the proteins were expressed in Sf9 insect cells. The presence of the M433 allele, W12/M433, or G12/M433 decreased 20-HETE production to 56-66% of control. In contrast these variants had no effect on the omega-hydroxylation of LTB(4). These findings are the first to identify a functional variant in the human CYP4F2 gene that alters the production of 20-HETE.
The process in which the volume of blood increases renal pressure and thereby results in both an increase in urine volume (diuresis) and an increase in the amount of sodium excreted in the urine (natriuresis).
Evidence
1:
Inferred from Expression PatternUniProtKB
J. Biol. Chem. 275, 4118-4126 (2000)[PubMed:10660572]
20-hydroxyeicosatetraenoic acid (20-HETE), an omega-hydroxylated arachidonic acid (AA) metabolite, elicits specific effects on kidney vascular and tubular function that, in turn, influence blood pressure control. The human kidney's capacity to convert AA to 20-HETE is unclear, however, as is the underlying P450 catalyst. Microsomes from human kidney cortex were found to convert AA to a single major product, namely 20-HETE, but failed to catalyze AA epoxygenation and midchain hydroxylation. Despite the monophasic nature of renal AA omega-hydroxylation kinetics, immunochemical studies revealed participation of two P450s, CYP4F2 and CYP4A11, since antibodies to these enzymes inhibited 20-HETE formation by 65. 9 +/- 17 and 32.5 +/- 14%, respectively. Western blotting confirmed abundant expression of these CYP4 proteins in human kidney and revealed that other AA-oxidizing P450s, including CYP2C8, CYP2C9, and CYP2E1, were not expressed. Immunocytochemistry showed CYP4F2 and CYP4A11 expression in only the S2 and S3 segments of proximal tubules in cortex and outer medulla. Our results demonstrate that CYP4F2 and CYP4A11 underlie conversion of AA to 20-HETE, a natriuretic and vasoactive eicosanoid, in human kidney. Considering their proximal tubular localization, these P450 enzymes may partake in pivotal renal functions, including the regulation of salt and water balance, and arterial blood pressure itself.
Any process that modulates the force with which blood travels through the circulatory system. The process is controlled by a balance of processes that increase pressure and decrease pressure.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
Arachidonic acid is a major fatty acid that can be metabolized by the cytochrome P450 enzyme to a number of bioactive eicosanoids. A major metabolite of this oxidation is 20-hydroxyeicosatetraenoic acid, which acts as a potent vasoconstrictor. However, in the kidney, its vasoconstrictor actions can be offset by its natriuretic properties. A guanine-to-adenine polymorphism in the CYP4F2 gene was associated with a reduction in 20-hydroxyeicosatetraenoic acid production in vitro. A thymidine-to-cytosine polymorphism in the CYP4A11 gene reduced catalytic activity by >50% in vitro and was associated with hypertension. The aim was to determine whether these 2 mutations are associated with urinary 20-hydroxyeicosatetraenoic acid excretion and blood pressure in humans. For the CYP4F2, 51% were homozygous for the G allele, 40% were carriers, and 9% were homozygous for the A allele. For CYP4A11, 72% were homozygous for the T allele, 25% were carriers, and 3% were homozygous for the C allele. The CYP4F2 GA/AA genotype was significantly associated with an increase in both 20-hydroxyeicosatetraenoic acid excretion and systolic blood pressure. The CYP4A11 CC/TC genotype was significantly associated with a reduction in 20-hydroxyeicosatetraenoic acid excretion but was not associated with blood pressure. We have demonstrated for the first time in humans that polymorphisms of the CYP4F2 and CYP4A11 genes have opposite effects on 20-hydroxyeicosatetraenoic acid excretion. The positive association between the CYP4F2 GA/AA genotype and both systolic blood pressure and 20-hydroxyeicosatetraenoic acid excretion strengthens a role for 20-hydroxyeicosatetraenoic acid in the modulation of blood pressure.
J. Biol. Chem. 275, 4118-4126 (2000)[PubMed:10660572]
20-hydroxyeicosatetraenoic acid (20-HETE), an omega-hydroxylated arachidonic acid (AA) metabolite, elicits specific effects on kidney vascular and tubular function that, in turn, influence blood pressure control. The human kidney's capacity to convert AA to 20-HETE is unclear, however, as is the underlying P450 catalyst. Microsomes from human kidney cortex were found to convert AA to a single major product, namely 20-HETE, but failed to catalyze AA epoxygenation and midchain hydroxylation. Despite the monophasic nature of renal AA omega-hydroxylation kinetics, immunochemical studies revealed participation of two P450s, CYP4F2 and CYP4A11, since antibodies to these enzymes inhibited 20-HETE formation by 65. 9 +/- 17 and 32.5 +/- 14%, respectively. Western blotting confirmed abundant expression of these CYP4 proteins in human kidney and revealed that other AA-oxidizing P450s, including CYP2C8, CYP2C9, and CYP2E1, were not expressed. Immunocytochemistry showed CYP4F2 and CYP4A11 expression in only the S2 and S3 segments of proximal tubules in cortex and outer medulla. Our results demonstrate that CYP4F2 and CYP4A11 underlie conversion of AA to 20-HETE, a natriuretic and vasoactive eicosanoid, in human kidney. Considering their proximal tubular localization, these P450 enzymes may partake in pivotal renal functions, including the regulation of salt and water balance, and arterial blood pressure itself.
J. Biol. Chem. 275, 4118-4126 (2000)[PubMed:10660572]
20-hydroxyeicosatetraenoic acid (20-HETE), an omega-hydroxylated arachidonic acid (AA) metabolite, elicits specific effects on kidney vascular and tubular function that, in turn, influence blood pressure control. The human kidney's capacity to convert AA to 20-HETE is unclear, however, as is the underlying P450 catalyst. Microsomes from human kidney cortex were found to convert AA to a single major product, namely 20-HETE, but failed to catalyze AA epoxygenation and midchain hydroxylation. Despite the monophasic nature of renal AA omega-hydroxylation kinetics, immunochemical studies revealed participation of two P450s, CYP4F2 and CYP4A11, since antibodies to these enzymes inhibited 20-HETE formation by 65. 9 +/- 17 and 32.5 +/- 14%, respectively. Western blotting confirmed abundant expression of these CYP4 proteins in human kidney and revealed that other AA-oxidizing P450s, including CYP2C8, CYP2C9, and CYP2E1, were not expressed. Immunocytochemistry showed CYP4F2 and CYP4A11 expression in only the S2 and S3 segments of proximal tubules in cortex and outer medulla. Our results demonstrate that CYP4F2 and CYP4A11 underlie conversion of AA to 20-HETE, a natriuretic and vasoactive eicosanoid, in human kidney. Considering their proximal tubular localization, these P450 enzymes may partake in pivotal renal functions, including the regulation of salt and water balance, and arterial blood pressure itself.
The cytochrome P450 gene 4 family (CYP4) consists of a group of over 63 members that omega-hydroxylate the terminal carbon of fatty acids. In mammals, six subfamilies have been identified and three of these subfamily members show a preference in the metabolism of short (C7-C10)-CYP4B, medium (C10-C16)-CYP4A, and long (C16-C26)-CYP4F, saturated, unsaturated and branched chain fatty acids. These omega-hydroxylated fatty acids are converted to dicarboxylic acids, which are preferentially metabolized by the peroxisome beta-oxidation system to shorter chain fatty acids that are transported to the mitochondria for complete oxidation or used either to supply energy for peripheral tissues during starvation or in lipid synthesis. The differential regulation of the CYP4A and CYP4F genes during fasting, by peroxisome proliferators and in non-alcoholic fatty liver disease (NAFLD) suggests different roles in lipid metabolism. The omega-hydroxylation and inactivation of pro-inflammatory eicosanoids by members of the CYP4F subfamily and the association of the CYP4F2 and CYP4F3 genes with inflammatory celiac disease indicate an important role in the resolution of inflammation. Several human diseases have been genetically linked to the expression CYP4 gene polymorphic variants, which may link human susceptibility to diseases of lipid metabolism and the activation and resolution phases of inflammation. Understanding how the CYP4 genes are regulated during the fasting and feeding cycles and by endogenous lipids will provide therapeutic avenues in the treatment of metabolic disorders of lipid metabolism and inflammation.
The chemical reactions and pathways involving vitamin E, tocopherol, which includes a series of eight structurally similar compounds. Alpha-tocopherol is the most active form in humans and is a powerful biological antioxidant.
Human cytochrome P450 4F2 (CYP4F2) catalyzes the ω-hydroxylation of the side chain of tocopherols (TOH) and tocotrienols (T3), the first step in their catabolism to polar metabolites excreted in urine. CYP4F2, in conjunction with α-TOH transfer protein, results in the conserved phenotype of selective retention of α-TOH. The purpose of this work was to determine the functional consequences of 2 common genetic variants in the human CYP4F2 gene on vitamin E-ω-hydroxylase specific activity using the 6 major dietary TOH and T3 as substrate. CYP4F2-mediated ω-hydroxylase specific activity was measured in microsomal preparations from insect cells that express wild-type or polymorphic variants of the human CYP4F2 protein. The W12G variant exhibited a greater enzyme specific activity (pmol product · min(-1) · pmol CYP4F2(-1)) compared with wild-type enzyme for both TOH and T3, 230-275% of wild-type toward α, γ, and δ-TOH and 350% of wild-type toward α, γ, and δ-T3. In contrast, the V433M variant had lower enzyme specific activity toward TOH (42-66% of wild type) but was without a significant effect on the metabolism of T3. Because CYP4F2 is the only enzyme currently shown to metabolize vitamin E in humans, the observed substrate-dependent alterations in enzyme activity associated with these genetic variants may result in alterations in vitamin E status in individuals carrying these mutations and constitute a source of variability in vitamin E status.
The chemical reactions and pathways resulting in the formation of any of the forms of vitamin K, quinone-derived vitamins which are involved in the synthesis of blood-clotting factors in mammals.
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
Neural prostheses aim to provide treatment options for individuals with nervous-system disease or injury. It is necessary, however, to increase the performance of such systems before they can be clinically viable for patients with motor dysfunction. One performance limitation is the presence of correlated trial-to-trial variability that can cause neural responses to wax and wane in concert as the subject is, for example, more attentive or more fatigued. If a system does not properly account for this variability, it may mistakenly interpret such variability as an entirely different intention by the subject. We report here the design and characterization of factor-analysis (FA)-based decoding algorithms that can contend with this confound. We characterize the decoders (classifiers) on experimental data where monkeys performed both a real reach task and a prosthetic cursor task while we recorded from 96 electrodes implanted in dorsal premotor cortex. The decoder attempts to infer the underlying factors that comodulate the neurons' responses and can use this information to substantially lower error rates (one of eight reach endpoint predictions) by <or=75% (e.g., approximately 20% total prediction error using traditional independent Poisson models reduced to approximately 5%). We also examine additional key aspects of these new algorithms: the effect of neural integration window length on performance, an extension of the algorithms to use Poisson statistics, and the effect of training set size on the decoding accuracy of test data. We found that FA-based methods are most effective for integration windows >150 ms, although still advantageous at shorter timescales, that Gaussian-based algorithms performed better than the analogous Poisson-based algorithms and that the FA algorithm is robust even with a limited amount of training data. We propose that FA-based methods are effective in modeling correlated trial-to-trial neural variability and can be used to substantially increase overall prosthetic system performance.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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