Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is one of the most common recessively inherited metabolic diseases in man. We have studied fibroblast cultures obtained from three patients with MCAD deficiency by sequencing the entire coding region of MCAD mRNA. A single A to G nucleotide replacement which resulted in lysine329-to-glutamic acid329 substitution of the MCAD protein was identified in all cultures. Furthermore, this point mutation was present in 91% (31 of 34) of mutant MCAD alleles, indicating that the majority of cases with MCAD deficiency are caused by this type of mutation.
Newborn screening (NBS) for medium-chain acyl-CoA dehydrogenase deficiency (MCADD) revealed a higher birth prevalence and genotypic variability than previously estimated, including numerous novel missense mutations in the ACADM gene. On average, these mutations are associated with milder biochemical phenotypes raising the question about their pathogenic relevance. In this study, we analyzed the impact of 10 ACADM mutations identified in NBS (A27V, Y42H, Y133H, R181C, R223G, D241G, K304E, R309K, I331T and R388S) on conformation, stability and enzyme kinetics of the corresponding proteins. Partial to total rescue of aggregation by co-overexpression of GroESL indicated protein misfolding. This was confirmed by accelerated thermal unfolding in all variants, as well as decreased proteolytic stability and accelerated thermal inactivation in most variants. Catalytic function varied from high residual activity to markedly decreased activity or substrate affinity. Mutations mapping to the beta-domain of the protein predisposed to severe destabilization. In silico structural analyses of the affected amino acid residues revealed involvement in functionally relevant networks. Taken together, our results substantiate the hypothesis of protein misfolding with loss-of-function being the common molecular basis in MCADD. Moreover, considerable structural alterations in all analyzed variants do not support the view that novel mutations found in NBS bear a lower risk of metabolic decompensation than that associated with mutations detected in clinically ascertained patients. Finally, the detailed insight into how ACADM missense mutations induce loss of MCAD function may provide guidance for risk assessment and counseling of patients, and in future may assist delineation of novel pharmacological strategies.
Interacting selectively and non-covalently with FAD, flavin-adenine dinucleotide, the coenzyme or the prosthetic group of various flavoprotein oxidoreductase enzymes, in either the oxidized form, FAD, or the reduced form, FADH2.
Newborn screening (NBS) for medium-chain acyl-CoA dehydrogenase deficiency (MCADD) revealed a higher birth prevalence and genotypic variability than previously estimated, including numerous novel missense mutations in the ACADM gene. On average, these mutations are associated with milder biochemical phenotypes raising the question about their pathogenic relevance. In this study, we analyzed the impact of 10 ACADM mutations identified in NBS (A27V, Y42H, Y133H, R181C, R223G, D241G, K304E, R309K, I331T and R388S) on conformation, stability and enzyme kinetics of the corresponding proteins. Partial to total rescue of aggregation by co-overexpression of GroESL indicated protein misfolding. This was confirmed by accelerated thermal unfolding in all variants, as well as decreased proteolytic stability and accelerated thermal inactivation in most variants. Catalytic function varied from high residual activity to markedly decreased activity or substrate affinity. Mutations mapping to the beta-domain of the protein predisposed to severe destabilization. In silico structural analyses of the affected amino acid residues revealed involvement in functionally relevant networks. Taken together, our results substantiate the hypothesis of protein misfolding with loss-of-function being the common molecular basis in MCADD. Moreover, considerable structural alterations in all analyzed variants do not support the view that novel mutations found in NBS bear a lower risk of metabolic decompensation than that associated with mutations detected in clinically ascertained patients. Finally, the detailed insight into how ACADM missense mutations induce loss of MCAD function may provide guidance for risk assessment and counseling of patients, and in future may assist delineation of novel pharmacological strategies.
Catalysis of the reaction: acyl-CoA + acceptor = 2,3-dehydroacyl-CoA + reduced acceptor, where the acyl group is a medium-chain fatty acid residue. A medium chain fatty acid is any fatty acid with a chain length of between C6 and C12.
Newborn screening (NBS) for medium-chain acyl-CoA dehydrogenase deficiency (MCADD) revealed a higher birth prevalence and genotypic variability than previously estimated, including numerous novel missense mutations in the ACADM gene. On average, these mutations are associated with milder biochemical phenotypes raising the question about their pathogenic relevance. In this study, we analyzed the impact of 10 ACADM mutations identified in NBS (A27V, Y42H, Y133H, R181C, R223G, D241G, K304E, R309K, I331T and R388S) on conformation, stability and enzyme kinetics of the corresponding proteins. Partial to total rescue of aggregation by co-overexpression of GroESL indicated protein misfolding. This was confirmed by accelerated thermal unfolding in all variants, as well as decreased proteolytic stability and accelerated thermal inactivation in most variants. Catalytic function varied from high residual activity to markedly decreased activity or substrate affinity. Mutations mapping to the beta-domain of the protein predisposed to severe destabilization. In silico structural analyses of the affected amino acid residues revealed involvement in functionally relevant networks. Taken together, our results substantiate the hypothesis of protein misfolding with loss-of-function being the common molecular basis in MCADD. Moreover, considerable structural alterations in all analyzed variants do not support the view that novel mutations found in NBS bear a lower risk of metabolic decompensation than that associated with mutations detected in clinically ascertained patients. Finally, the detailed insight into how ACADM missense mutations induce loss of MCAD function may provide guidance for risk assessment and counseling of patients, and in future may assist delineation of novel pharmacological strategies.
J. Biol. Chem. 265, 7116-7119 (1990)[PubMed:1970566]
The cDNA of human medium chain acyl-CoA dehydrogenase (MCADH) was modified by in vitro mutagenesis, and the sequence encoding the mature form of MCADH was introduced into an inducible expression plasmid. We observed synthesis of the protein in Escherichia coli cells transformed with this plasmid with measurable MCADH enzyme activity in cell extracts. Glutamic acid 376, which has been proposed by Powell and Thorpe (Powell, P. J., and Thorpe, J. (1988) Biochemistry 27, 8022-8028) as an essential residue and the proton-abstracting base at the active site of the enzyme, was mutated to glutamine. After expression in bacteria of this plasmid, the corresponding extracts show no detectable MCADH activity, although mutant MCADH-protein production was detected by protein immunoblots. The mature enzyme and the Gln376 mutant were purified to apparent homogeneity. The wild-type enzyme is a yellow protein due to the content of stoichiometric FAD and had a specific activity which is 50% of MCADH purified from pig kidney. The Gln376 mutant is devoid of activity (less than 0.02% that of wild type, expressed enzyme) and is green because of bound CoA persulfide. Properties of the mutant enzyme suggest that the Glu376----Gln change specifically affects substrate binding. These results prove that Glu376 plays an important role in the initial step of dehydrogenation catalysis.
A series of experiments has established the molecular defect in the medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCAD) gene in a family with MCAD deficiency. Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD, and of mRNA with the correct size of 2.4 kb, indicated a point-mutation in the coding region of the MCAD gene to be disease-causing. Consequently, cloning and DNA sequencing of polymerase chain reaction (PCR) amplified complementary DNA (cDNA) from messenger RNA of fibroblasts from the patient and family members were performed. All clones sequenced from the patient exhibited a single base substitution from adenine (A) to guanine (G) at position 985 in the MCAD cDNA as the only consistent base-variation compared with control cDNA. In contrast, the parents contained cDNA with the normal and the mutated sequence, revealing their obligate carrier status. Allelic homozygosity in the patient and heterozygosity for the mutation in the parents were established by a modified PCR reaction, introducing a cleavage site for the restriction endonuclease NcoI into amplified genomic DNA containing G985. The same assay consistently revealed A985 in genomic DNA from 26 control individuals. The A to G mutation was introduced into an E. coli expression vector producing mutant MCAD, which was demonstrated to be inactive, probably because of the inability to form active tetrameric MCAD. All the experiments are consistent with the contention that the G985 mutation, resulting in a lysine to glutamate shift at position 329 in the MCAD polypeptide chain, is the genetic cause of MCAD deficiency in this family. We found the same mutation in homozygous form in 11 out of 12 other patients with verified MCAD deficiency.
The process in which a cardiac muscle precursor cell acquires specialized features of a cardiac muscle cell. Cardiac muscle cells are striated muscle cells that are responsible for heart contraction.
The chemical reactions and pathways resulting in the formation of carnitine (hydroxy-trimethyl aminobutyric acid), a compound that participates in the transfer of acyl groups across the inner mitochondrial membrane.
Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is probably the most common inborn error of fatty acid oxidation (FAO). Routine L-carnitine supplementation in the treatment of MCADD is controversial. To establish the effects of L-carnitine supplementation during prolonged moderate-intensity exercise in MCADD, five patients and three control subjects were studied during 2 hours of moderate-intensity exercise after a 12-hour fast. Patients were studied twice, once with and once without L-carnitine supplementation (50 mg/kg per day). Blood samples were collected before, during and after exercise, and analysed for routine parameters, acylcarnitines and carnitine biosynthesis intermediates. Urine was collected before and after exercise, and analysed for acylcarnitines. All patients were able to complete the exercise test without any apparent clinical or biochemical adverse effects, even without L-carnitine supplementation. A significant rise in plasma free fatty acids and octanoylcarnitine levels during exercise was seen in all patients, indicating a substantial increase in FAO during exercise. Octanoylcarnitine levels in plasma were significantly higher in patients with L-carnitine supplementation, suggesting increased clearance of accumulating acylcarnitines. A statistically significant increase of plasma and urinary free carnitine levels, as well as of plasma gamma-butyrobetaine was seen in MCADD patients without L-carnitine supplementation. These data suggest an increase in carnitine biosynthesis. In conclusion, although L-carnitine supplementation may promote clearance of accumulating acylcarnitines during moderate-intensity exercise, no apparent beneficial effect of this supplementation on clinical and biochemical parameters was observed in MCADD patients. Our results suggest that MCADD patients are able to increase carnitine biosynthesis during exercise to compensate for carnitine losses.
Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is probably the most common inborn error of fatty acid oxidation (FAO). Routine L-carnitine supplementation in the treatment of MCADD is controversial. To establish the effects of L-carnitine supplementation during prolonged moderate-intensity exercise in MCADD, five patients and three control subjects were studied during 2 hours of moderate-intensity exercise after a 12-hour fast. Patients were studied twice, once with and once without L-carnitine supplementation (50 mg/kg per day). Blood samples were collected before, during and after exercise, and analysed for routine parameters, acylcarnitines and carnitine biosynthesis intermediates. Urine was collected before and after exercise, and analysed for acylcarnitines. All patients were able to complete the exercise test without any apparent clinical or biochemical adverse effects, even without L-carnitine supplementation. A significant rise in plasma free fatty acids and octanoylcarnitine levels during exercise was seen in all patients, indicating a substantial increase in FAO during exercise. Octanoylcarnitine levels in plasma were significantly higher in patients with L-carnitine supplementation, suggesting increased clearance of accumulating acylcarnitines. A statistically significant increase of plasma and urinary free carnitine levels, as well as of plasma gamma-butyrobetaine was seen in MCADD patients without L-carnitine supplementation. These data suggest an increase in carnitine biosynthesis. In conclusion, although L-carnitine supplementation may promote clearance of accumulating acylcarnitines during moderate-intensity exercise, no apparent beneficial effect of this supplementation on clinical and biochemical parameters was observed in MCADD patients. Our results suggest that MCADD patients are able to increase carnitine biosynthesis during exercise to compensate for carnitine losses.
A fatty acid oxidation process that results in the complete oxidation of a long-chain fatty acid. Fatty acid beta-oxidation begins with the addition of coenzyme A to a fatty acid, and occurs by successive cycles of reactions during each of which the fatty acid is shortened by a two-carbon fragment removed as acetyl coenzyme A; the cycle continues until only two or three carbons remain (as acetyl-CoA or propionyl-CoA respectively).
Evidence
1:
Inferred from Mutant PhenotypeUniProtKB
Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is one of the most common recessively inherited metabolic diseases in man. We have studied fibroblast cultures obtained from three patients with MCAD deficiency by sequencing the entire coding region of MCAD mRNA. A single A to G nucleotide replacement which resulted in lysine329-to-glutamic acid329 substitution of the MCAD protein was identified in all cultures. Furthermore, this point mutation was present in 91% (31 of 34) of mutant MCAD alleles, indicating that the majority of cases with MCAD deficiency are caused by this type of mutation.
A fatty acid beta-oxidation pathway in which the initial step of each oxidation cycle, which converts an acyl-CoA to a trans-2-enoyl-CoA, is catalyzed by acyl-CoA dehydrogenase; the electrons removed by oxidation pass through the respiratory chain to oxygen and leave H2O as the product. Fatty acid beta-oxidation begins with the addition of coenzyme A to a fatty acid, and ends when only two or three carbons remain (as acetyl-CoA or propionyl-CoA respectively).
Newborn screening (NBS) for medium-chain acyl-CoA dehydrogenase deficiency (MCADD) revealed a higher birth prevalence and genotypic variability than previously estimated, including numerous novel missense mutations in the ACADM gene. On average, these mutations are associated with milder biochemical phenotypes raising the question about their pathogenic relevance. In this study, we analyzed the impact of 10 ACADM mutations identified in NBS (A27V, Y42H, Y133H, R181C, R223G, D241G, K304E, R309K, I331T and R388S) on conformation, stability and enzyme kinetics of the corresponding proteins. Partial to total rescue of aggregation by co-overexpression of GroESL indicated protein misfolding. This was confirmed by accelerated thermal unfolding in all variants, as well as decreased proteolytic stability and accelerated thermal inactivation in most variants. Catalytic function varied from high residual activity to markedly decreased activity or substrate affinity. Mutations mapping to the beta-domain of the protein predisposed to severe destabilization. In silico structural analyses of the affected amino acid residues revealed involvement in functionally relevant networks. Taken together, our results substantiate the hypothesis of protein misfolding with loss-of-function being the common molecular basis in MCADD. Moreover, considerable structural alterations in all analyzed variants do not support the view that novel mutations found in NBS bear a lower risk of metabolic decompensation than that associated with mutations detected in clinically ascertained patients. Finally, the detailed insight into how ACADM missense mutations induce loss of MCAD function may provide guidance for risk assessment and counseling of patients, and in future may assist delineation of novel pharmacological strategies.
Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is probably the most common inborn error of fatty acid oxidation (FAO). Routine L-carnitine supplementation in the treatment of MCADD is controversial. To establish the effects of L-carnitine supplementation during prolonged moderate-intensity exercise in MCADD, five patients and three control subjects were studied during 2 hours of moderate-intensity exercise after a 12-hour fast. Patients were studied twice, once with and once without L-carnitine supplementation (50 mg/kg per day). Blood samples were collected before, during and after exercise, and analysed for routine parameters, acylcarnitines and carnitine biosynthesis intermediates. Urine was collected before and after exercise, and analysed for acylcarnitines. All patients were able to complete the exercise test without any apparent clinical or biochemical adverse effects, even without L-carnitine supplementation. A significant rise in plasma free fatty acids and octanoylcarnitine levels during exercise was seen in all patients, indicating a substantial increase in FAO during exercise. Octanoylcarnitine levels in plasma were significantly higher in patients with L-carnitine supplementation, suggesting increased clearance of accumulating acylcarnitines. A statistically significant increase of plasma and urinary free carnitine levels, as well as of plasma gamma-butyrobetaine was seen in MCADD patients without L-carnitine supplementation. These data suggest an increase in carnitine biosynthesis. In conclusion, although L-carnitine supplementation may promote clearance of accumulating acylcarnitines during moderate-intensity exercise, no apparent beneficial effect of this supplementation on clinical and biochemical parameters was observed in MCADD patients. Our results suggest that MCADD patients are able to increase carnitine biosynthesis during exercise to compensate for carnitine losses.
A series of experiments has established the molecular defect in the medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCAD) gene in a family with MCAD deficiency. Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD, and of mRNA with the correct size of 2.4 kb, indicated a point-mutation in the coding region of the MCAD gene to be disease-causing. Consequently, cloning and DNA sequencing of polymerase chain reaction (PCR) amplified complementary DNA (cDNA) from messenger RNA of fibroblasts from the patient and family members were performed. All clones sequenced from the patient exhibited a single base substitution from adenine (A) to guanine (G) at position 985 in the MCAD cDNA as the only consistent base-variation compared with control cDNA. In contrast, the parents contained cDNA with the normal and the mutated sequence, revealing their obligate carrier status. Allelic homozygosity in the patient and heterozygosity for the mutation in the parents were established by a modified PCR reaction, introducing a cleavage site for the restriction endonuclease NcoI into amplified genomic DNA containing G985. The same assay consistently revealed A985 in genomic DNA from 26 control individuals. The A to G mutation was introduced into an E. coli expression vector producing mutant MCAD, which was demonstrated to be inactive, probably because of the inability to form active tetrameric MCAD. All the experiments are consistent with the contention that the G985 mutation, resulting in a lysine to glutamate shift at position 329 in the MCAD polypeptide chain, is the genetic cause of MCAD deficiency in this family. We found the same mutation in homozygous form in 11 out of 12 other patients with verified MCAD deficiency.
The chemical reactions and pathways resulting in the formation of glycogen, a polydisperse, highly branched glucan composed of chains of D-glucose residues.
The process whose specific outcome is the progression of the liver over time, from its formation to the mature structure. The liver is an exocrine gland which secretes bile and functions in metabolism of protein and carbohydrate and fat, synthesizes substances involved in the clotting of the blood, synthesizes vitamin A, detoxifies poisonous substances, stores glycogen, and breaks down worn-out erythrocytes.
J. Biol. Chem. 265, 7116-7119 (1990)[PubMed:1970566]
The cDNA of human medium chain acyl-CoA dehydrogenase (MCADH) was modified by in vitro mutagenesis, and the sequence encoding the mature form of MCADH was introduced into an inducible expression plasmid. We observed synthesis of the protein in Escherichia coli cells transformed with this plasmid with measurable MCADH enzyme activity in cell extracts. Glutamic acid 376, which has been proposed by Powell and Thorpe (Powell, P. J., and Thorpe, J. (1988) Biochemistry 27, 8022-8028) as an essential residue and the proton-abstracting base at the active site of the enzyme, was mutated to glutamine. After expression in bacteria of this plasmid, the corresponding extracts show no detectable MCADH activity, although mutant MCADH-protein production was detected by protein immunoblots. The mature enzyme and the Gln376 mutant were purified to apparent homogeneity. The wild-type enzyme is a yellow protein due to the content of stoichiometric FAD and had a specific activity which is 50% of MCADH purified from pig kidney. The Gln376 mutant is devoid of activity (less than 0.02% that of wild type, expressed enzyme) and is green because of bound CoA persulfide. Properties of the mutant enzyme suggest that the Glu376----Gln change specifically affects substrate binding. These results prove that Glu376 plays an important role in the initial step of dehydrogenation catalysis.
J. Biol. Chem. 265, 7116-7119 (1990)[PubMed:1970566]
The cDNA of human medium chain acyl-CoA dehydrogenase (MCADH) was modified by in vitro mutagenesis, and the sequence encoding the mature form of MCADH was introduced into an inducible expression plasmid. We observed synthesis of the protein in Escherichia coli cells transformed with this plasmid with measurable MCADH enzyme activity in cell extracts. Glutamic acid 376, which has been proposed by Powell and Thorpe (Powell, P. J., and Thorpe, J. (1988) Biochemistry 27, 8022-8028) as an essential residue and the proton-abstracting base at the active site of the enzyme, was mutated to glutamine. After expression in bacteria of this plasmid, the corresponding extracts show no detectable MCADH activity, although mutant MCADH-protein production was detected by protein immunoblots. The mature enzyme and the Gln376 mutant were purified to apparent homogeneity. The wild-type enzyme is a yellow protein due to the content of stoichiometric FAD and had a specific activity which is 50% of MCADH purified from pig kidney. The Gln376 mutant is devoid of activity (less than 0.02% that of wild type, expressed enzyme) and is green because of bound CoA persulfide. Properties of the mutant enzyme suggest that the Glu376----Gln change specifically affects substrate binding. These results prove that Glu376 plays an important role in the initial step of dehydrogenation catalysis.
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.
A series of experiments has established the molecular defect in the medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCAD) gene in a family with MCAD deficiency. Demonstration of intra-mitochondrial mature MCAD indistinguishable in size (42.5-kDa) from control MCAD, and of mRNA with the correct size of 2.4 kb, indicated a point-mutation in the coding region of the MCAD gene to be disease-causing. Consequently, cloning and DNA sequencing of polymerase chain reaction (PCR) amplified complementary DNA (cDNA) from messenger RNA of fibroblasts from the patient and family members were performed. All clones sequenced from the patient exhibited a single base substitution from adenine (A) to guanine (G) at position 985 in the MCAD cDNA as the only consistent base-variation compared with control cDNA. In contrast, the parents contained cDNA with the normal and the mutated sequence, revealing their obligate carrier status. Allelic homozygosity in the patient and heterozygosity for the mutation in the parents were established by a modified PCR reaction, introducing a cleavage site for the restriction endonuclease NcoI into amplified genomic DNA containing G985. The same assay consistently revealed A985 in genomic DNA from 26 control individuals. The A to G mutation was introduced into an E. coli expression vector producing mutant MCAD, which was demonstrated to be inactive, probably because of the inability to form active tetrameric MCAD. All the experiments are consistent with the contention that the G985 mutation, resulting in a lysine to glutamate shift at position 329 in the MCAD polypeptide chain, is the genetic cause of MCAD deficiency in this family. We found the same mutation in homozygous form in 11 out of 12 other patients with verified MCAD deficiency.
The process whose specific outcome is the progression of the organism over time, from the completion of embryonic development to the mature structure. See embryonic development.
Any process that modulates the frequency, rate or extent of gluconeogenesis, the formation of glucose from noncarbohydrate precursors, such as pyruvate, amino acids and glycerol.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a cold stimulus, a temperature stimulus below the optimal temperature for that organism.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a starvation stimulus, deprivation of nourishment.
IEAOrtholog Compara
Enzymatic activity
This protein acts as an enzyme. It is known to catalyze the following reaction
EC 1.3.8.7: A medium-chain acyl-CoA + electron-transfer flavoprotein ⇄ a medium-chain trans-2,3-dehydroacyl-CoA + reduced electron-transfer flavoprotein.
A number of straight-chain acyl-CoA dehydrogenases of different substrate specificities are present in mammalian tissues.
CuratedUniProtKB
Utilizes the electron transfer flavoprotein (ETF) as electron acceptor that transfers the electrons to the main mitochondrial respiratory chain via ETF-ubiquinone oxidoreductase (ETF dehydrogenase).
Protein involved in the biochemical reactions with fatty acids. Fatty acids are long chain organic acids of the general formula CH3(CnHx)COOH. They are constituents of lipids and can be saturated or unsaturated. The esterified forms are important both as energy storage molecules and structural molecules.
Protein involved in the biochemical reactions of lipids. Lipids are a diverse class of compounds which are insoluble in water but soluble in organic solvents. They include fats, oils, triacylglycerols, fatty acids, glycolipids, phospholipids and steroids.
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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