Protein also known as:
Hageman factor (HAF).
Cleaved into:
Beta-factor XIIa part 1; Beta-factor XIIa part 2; Coagulation factor XIIa heavy chain; Coagulation factor XIIa light chain.
Factor XII is a serum glycoprotein that participates in the initiation of blood coagulation, fibrinolysis, and the generation of bradykinin and angiotensin. Prekallikrein is cleaved by factor XII to form kallikrein, which then cleaves factor XII first to alpha-factor XIIa and then trypsin cleaves it to beta-factor XIIa. Alpha-factor XIIa activates factor XI to factor XIa.
Histidine-rich glycoprotein (HRG) circulates in plasma at a concentration of 2μM and binds plasminogen, fibrinogen, and thrombospondin. Despite these interactions, the physiologic role of HRG is unknown. Previous studies have shown that mice and humans deficient in HRG have shortened plasma clotting times. To better understand this phenomenon, we examined the effect of HRG on clotting tests. HRG prolongs the activated partial thromboplastin time in a concentration-dependent fashion but has no effect on tissue factor-induced clotting, localizing its effect to the contact pathway. Plasma immunodepleted of HRG exhibits a shortened activated partial thromboplastin time that is restored to baseline with HRG replenishment. To explore how HRG affects the contact pathway, we examined its binding to factors XII, XIIa, XI, and XIa. HRG binds factor XIIa with high affinity, an interaction that is enhanced in the presence of Zn²(+), but does not bind factors XII, XI, or XIa. In addition, HRG inhibits autoactivation of factor XII and factor XIIa-mediated activation of factor XI. These results suggest that, by binding to factor XIIa, HRG modulates the intrinsic pathway of coagulation, particularly in the vicinity of a thrombus where platelet release of HRG and Zn²(+) will promote this interaction.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
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
Proc. Natl. Acad. Sci. U.S.A. 93, 8552-8557 (1996)[PubMed:8710908]
High molecular weight kininogen (HK) and factor XII are known to bind to human umbilical vein endothelial cells (HUVEC) in a zinc-dependent and saturable manner indicating that HUVEC express specific binding site(s) for those proteins. However, identification and immunochemical characterization of the putative receptor site(s) has not been previously accomplished. In this report, we have identified a cell surface glycoprotein that is a likely candidate for the HK binding site on HUVECs. When solubilized HUVEC membranes were subjected to an HK-affinity column in the presence or absence of 50 microM ZnCl2 and the bound membrane proteins eluted, a single major protein peak was obtained only in the presence of zinc. SDS/PAGE analysis and silver staining of the protein peak revealed this protein to be 33 kDa and partial sequence analysis matched the NH2 terminus of gC1q-R, a membrane glycoprotein that binds to the globular "heads" of C1q. Two other minor proteins of approximately 70 kDa and 45 kDa were also obtained. Upon analysis by Western blotting, the 33-kDa band was found to react with several monoclonal antibodies (mAbs) recognizing different epitopes on gC1q-R. Ligand and dot blot analyses revealed zinc-dependent binding of biotinylated HK as well as biotinylated factor XII to the isolated 33-kDa HUVEC molecule as well as recombinant gC1q-R. In addition, binding of 125I-HK to HUVEC cells was inhibited by selected monoclonal anti-gC1q-R antibodies. C1q, however, did not inhibit 125I-HK binding to HUVEC nor did those monoclonals known to inhibit C1q binding to gC1q-R. Taken together, the data suggest that HK (and factor XII) bind to HUVECs via a 33-kDa cell surface glycoprotein that appears to be identical to gC1q-R but interact with a site on gC1q-R distinct from that which binds C1q.
Evidence
2:
Inferred from Physical InteractionUniProtKB
Histidine-rich glycoprotein (HRG) circulates in plasma at a concentration of 2μM and binds plasminogen, fibrinogen, and thrombospondin. Despite these interactions, the physiologic role of HRG is unknown. Previous studies have shown that mice and humans deficient in HRG have shortened plasma clotting times. To better understand this phenomenon, we examined the effect of HRG on clotting tests. HRG prolongs the activated partial thromboplastin time in a concentration-dependent fashion but has no effect on tissue factor-induced clotting, localizing its effect to the contact pathway. Plasma immunodepleted of HRG exhibits a shortened activated partial thromboplastin time that is restored to baseline with HRG replenishment. To explore how HRG affects the contact pathway, we examined its binding to factors XII, XIIa, XI, and XIa. HRG binds factor XIIa with high affinity, an interaction that is enhanced in the presence of Zn²(+), but does not bind factors XII, XI, or XIa. In addition, HRG inhibits autoactivation of factor XII and factor XIIa-mediated activation of factor XI. These results suggest that, by binding to factor XIIa, HRG modulates the intrinsic pathway of coagulation, particularly in the vicinity of a thrombus where platelet release of HRG and Zn²(+) will promote this interaction.
Catalysis of the hydrolysis of a peptide bond not more than three residues from the N-terminus of a polypeptide chain by a catalytic mechanism that involves a catalytic triad consisting of a serine nucleophile that is activated by a proton relay involving an acidic residue (e.g. aspartate or glutamate) and a basic residue (usually histidine).
Catalysis of the hydrolysis of internal, alpha-peptide bonds in a polypeptide chain by a catalytic mechanism that involves a catalytic triad consisting of a serine nucleophile that is activated by a proton relay involving an acidic residue (e.g. aspartate or glutamate) and a basic residue (usually histidine).
J. Clin. Invest. 68, 1028-1035 (1981)[PubMed:6793628]
We have previously described two unrelated individuals with homozygous Hageman trait (Factor XII deficiency) whose plasmas contained nonfunctional material immunologically indistinguishable from normal Hageman factor (HF). Abnormal HF from the plasma of one these subjects has now been purified to homogeneity, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, alkaline disc gel electrophoresis, and immunoelectrophoresis. Purified abnormal HF had no clot-promoting activity, but showed the same specific antigenicity as purified normal HF by an immunoassay. The abnormal HF was of a single chain polypeptide with the same molecular weight (80,000) as normal HF and was positively stained by periodic acid-Schiff reagent. Both normal and abnormal HF had similar amino acid compositions and isoelectric points (pI 6.5 approximately 7.1). When 125I-labeled abnormal HF and 131I-labeled normal HF were mixed with normal plasma and exposed to glass, both HF underwent an identical pattern of cleavage, yielding 52,000- and 30,000-mol wt fragments. Similarly, abnormal HF was fragmented by trypsin in the same way as normal HF, but no prekallikrein-activating activity was generated after cleavage. [3H]Diisopropyl phosphorofluoridate was incorporated into a 29,000-mol wt fragment of the trypsin-cleaved normal HF, but not into that of the trypsin-cleaved abnormal HF. These data suggest that the molecular defect in this abnormal HF resides at or near the active site serine residue in the 30,000-mol wt part of the molecule.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
A protein activation cascade that contributes to blood coagulation and consists of the interactions among high molecular weight kininogen, prekallikrein, and factor XII that lead to the activation of clotting factor X.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
Any process that activates Factor XII (Hageman factor). Factor XII is a protein synthesized by the liver that circulates in an inactive form until it encounters collagen or basement membrane or activated platelets (as occurs at the site of endothelial injury). Factor XII then undergoes a conformational change (becoming factor XIIa), exposing an active serine center that can subsequently cleave protein substrates and activate a variety of mediator systems. Factor XII is a participant in the clotting cascade as well as the kinin cascade.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
Proc. Natl. Acad. Sci. U.S.A. 86, 8319-8322 (1989)[PubMed:2510163]
Structural studies on a congenital abnormal coagulation factor XII (Hageman factor), factor XII Washington D.C., have been performed to identify the defect responsible for its lack of procoagulant activity. Amino acid sequence analysis of a tryptic peptide isolated from the abnormal factor XII indicated that Cys-571 (equivalent to Cys-220 in the chymotrypsin numbering system) had been replaced by serine. No other substitutions in the active-site triad--namely, His-393, Asp-442, and Ser-544--were found. We propose that the Cys-571----Ser replacement found in this factor XII variant destroys the formation of the disulfide linkage between Cys-540 and Cys-571, giving rise to an altered conformation of the active-site serine residue or the secondary substrate-binding site and, thus, leads to the loss of enzyme activity.
A series of reactions that takes place outside the cell occurring in response to tissue damage and initiated within blood plasma by the action of activated Factor XII (Hageman Factor) on prekallikrein to convert it to plasma kallikrein, and the subsequent reaction of plasma kallikrein with high molecular weight kininogen. The ultimate product of the plasma kallikrein-kinin cascade is bradykinin, an agent known to induce smooth muscle contraction, vasoconstriction, and increased vascular permeability.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
J. Clin. Invest. 68, 1028-1035 (1981)[PubMed:6793628]
We have previously described two unrelated individuals with homozygous Hageman trait (Factor XII deficiency) whose plasmas contained nonfunctional material immunologically indistinguishable from normal Hageman factor (HF). Abnormal HF from the plasma of one these subjects has now been purified to homogeneity, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, alkaline disc gel electrophoresis, and immunoelectrophoresis. Purified abnormal HF had no clot-promoting activity, but showed the same specific antigenicity as purified normal HF by an immunoassay. The abnormal HF was of a single chain polypeptide with the same molecular weight (80,000) as normal HF and was positively stained by periodic acid-Schiff reagent. Both normal and abnormal HF had similar amino acid compositions and isoelectric points (pI 6.5 approximately 7.1). When 125I-labeled abnormal HF and 131I-labeled normal HF were mixed with normal plasma and exposed to glass, both HF underwent an identical pattern of cleavage, yielding 52,000- and 30,000-mol wt fragments. Similarly, abnormal HF was fragmented by trypsin in the same way as normal HF, but no prekallikrein-activating activity was generated after cleavage. [3H]Diisopropyl phosphorofluoridate was incorporated into a 29,000-mol wt fragment of the trypsin-cleaved normal HF, but not into that of the trypsin-cleaved abnormal HF. These data suggest that the molecular defect in this abnormal HF resides at or near the active site serine residue in the 30,000-mol wt part of the molecule.
J. Clin. Invest. 68, 1028-1035 (1981)[PubMed:6793628]
We have previously described two unrelated individuals with homozygous Hageman trait (Factor XII deficiency) whose plasmas contained nonfunctional material immunologically indistinguishable from normal Hageman factor (HF). Abnormal HF from the plasma of one these subjects has now been purified to homogeneity, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, alkaline disc gel electrophoresis, and immunoelectrophoresis. Purified abnormal HF had no clot-promoting activity, but showed the same specific antigenicity as purified normal HF by an immunoassay. The abnormal HF was of a single chain polypeptide with the same molecular weight (80,000) as normal HF and was positively stained by periodic acid-Schiff reagent. Both normal and abnormal HF had similar amino acid compositions and isoelectric points (pI 6.5 approximately 7.1). When 125I-labeled abnormal HF and 131I-labeled normal HF were mixed with normal plasma and exposed to glass, both HF underwent an identical pattern of cleavage, yielding 52,000- and 30,000-mol wt fragments. Similarly, abnormal HF was fragmented by trypsin in the same way as normal HF, but no prekallikrein-activating activity was generated after cleavage. [3H]Diisopropyl phosphorofluoridate was incorporated into a 29,000-mol wt fragment of the trypsin-cleaved normal HF, but not into that of the trypsin-cleaved abnormal HF. These data suggest that the molecular defect in this abnormal HF resides at or near the active site serine residue in the 30,000-mol wt part of the molecule.
Any process that activates, maintains or increases the frequency, rate or extent of fibrinolysis, an ongoing process that solubilizes fibrin, resulting in the removal of small blood clots.
Human coagulation factor XI has been purified, and upon activation with Hageman factor fragments, was found to convert the fibrinolytic proenzyme plasminogen to plasmin. This proactivator activity was shown to be functionally and antigenically distinct from prekallikrein. When the gamma-globulin fractions of plasma deficient in Hageman factor, prekallikrein and factor XI were isolated, factor-XI-deficient plasma possessed two-thirds of the plasminogen proactivator activity of the Hageman-factor-deficient plasma, while prekallikrein deficient plasma had only one-third of the plasminogen proactivator activity. Thus, the Hageman-factor-dependent plasminogen proactivator previously reported to be present in the gamma-globulin fraction of normal human plasma is a function of prekallikrein and factor XI, while the activity observed in prekallikrein-deficient plasma is attributable to factor XI. When compared utilizing digestion of iodinated fibrin, prekallikrein and factor XIa had similar potency per active site; they were, however, far less active than urokinase.
Any process that increases the rate, frequency or extent of plasminogen activation. Plasminogen activation is the process in which plasminogen is processed to plasmin.
Human coagulation factor XI has been purified, and upon activation with Hageman factor fragments, was found to convert the fibrinolytic proenzyme plasminogen to plasmin. This proactivator activity was shown to be functionally and antigenically distinct from prekallikrein. When the gamma-globulin fractions of plasma deficient in Hageman factor, prekallikrein and factor XI were isolated, factor-XI-deficient plasma possessed two-thirds of the plasminogen proactivator activity of the Hageman-factor-deficient plasma, while prekallikrein deficient plasma had only one-third of the plasminogen proactivator activity. Thus, the Hageman-factor-dependent plasminogen proactivator previously reported to be present in the gamma-globulin fraction of normal human plasma is a function of prekallikrein and factor XI, while the activity observed in prekallikrein-deficient plasma is attributable to factor XI. When compared utilizing digestion of iodinated fibrin, prekallikrein and factor XIa had similar potency per active site; they were, however, far less active than urokinase.
Processing which a protein carries out itself. This involves actions such as the autolytic removal of residues to generate the mature form of the protein.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
Any protein maturation process achieved by the cleavage of a peptide bond or bonds within a protein. Protein maturation is the process leading to the attainment of the full functional capacity of a protein.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
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 misfolded protein stimulus.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
When blood is exposed to negatively charged surface materials such as glass, an enzymatic cascade known as the contact system becomes activated. This cascade is initiated by autoactivation of Factor XII and leads to both coagulation (via Factor XI) and an inflammatory response (via the kallikrein-kinin system). However, while Factor XII is important for coagulation in vitro, it is not important for physiological hemostasis, so the physiological role of the contact system remains elusive. Using patient blood samples and isolated proteins, we identified a novel class of Factor XII activators. Factor XII was activated by misfolded protein aggregates that formed by denaturation or by surface adsorption, which specifically led to the activation of the kallikrein-kinin system without inducing coagulation. Consistent with this, we found that Factor XII, but not Factor XI, was activated and kallikrein was formed in blood from patients with systemic amyloidosis, a disease marked by the accumulation and deposition of misfolded plasma proteins. These results show that the kallikrein-kinin system can be activated by Factor XII, in a process separate from the coagulation cascade, and point to a protective role for Factor XII following activation by misfolded protein aggregates.
Human coagulation factor XI has been purified, and upon activation with Hageman factor fragments, was found to convert the fibrinolytic proenzyme plasminogen to plasmin. This proactivator activity was shown to be functionally and antigenically distinct from prekallikrein. When the gamma-globulin fractions of plasma deficient in Hageman factor, prekallikrein and factor XI were isolated, factor-XI-deficient plasma possessed two-thirds of the plasminogen proactivator activity of the Hageman-factor-deficient plasma, while prekallikrein deficient plasma had only one-third of the plasminogen proactivator activity. Thus, the Hageman-factor-dependent plasminogen proactivator previously reported to be present in the gamma-globulin fraction of normal human plasma is a function of prekallikrein and factor XI, while the activity observed in prekallikrein-deficient plasma is attributable to factor XI. When compared utilizing digestion of iodinated fibrin, prekallikrein and factor XIa had similar potency per active site; they were, however, far less active than urokinase.
J. Clin. Invest. 68, 1028-1035 (1981)[PubMed:6793628]
We have previously described two unrelated individuals with homozygous Hageman trait (Factor XII deficiency) whose plasmas contained nonfunctional material immunologically indistinguishable from normal Hageman factor (HF). Abnormal HF from the plasma of one these subjects has now been purified to homogeneity, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, alkaline disc gel electrophoresis, and immunoelectrophoresis. Purified abnormal HF had no clot-promoting activity, but showed the same specific antigenicity as purified normal HF by an immunoassay. The abnormal HF was of a single chain polypeptide with the same molecular weight (80,000) as normal HF and was positively stained by periodic acid-Schiff reagent. Both normal and abnormal HF had similar amino acid compositions and isoelectric points (pI 6.5 approximately 7.1). When 125I-labeled abnormal HF and 131I-labeled normal HF were mixed with normal plasma and exposed to glass, both HF underwent an identical pattern of cleavage, yielding 52,000- and 30,000-mol wt fragments. Similarly, abnormal HF was fragmented by trypsin in the same way as normal HF, but no prekallikrein-activating activity was generated after cleavage. [3H]Diisopropyl phosphorofluoridate was incorporated into a 29,000-mol wt fragment of the trypsin-cleaved normal HF, but not into that of the trypsin-cleaved abnormal HF. These data suggest that the molecular defect in this abnormal HF resides at or near the active site serine residue in the 30,000-mol wt part of the molecule.
Protein involved in blood clotting, a complex enzymatic cascade, in which the activated form of one factor catalyzes the activation of the next factor. Both, the extrinsic clotting pathway, induced by a damaged surface, and the intrinsic pathway, induced by a trauma, converge in a final common pathway to form cross-linked fibrin clots.
Enzyme which catalyzes hydrolysis reaction, i.e. the addition of the hydrogen and hydroxyl ions of water to a molecule with its consequent splitting into two or more simpler molecules.
Proteolytic enzyme with a serine residue (Ser) in its active site. The reactivity of the serine residue is ensured by the vicinity of a histidine and an aspartate residue (catalytic triad), all three residues are required for the charge relay system to take place.
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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