Factor Xa: Difference between revisions
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[[Image:Coagulation full.svg.png|thumb| | <StructureSection load='2PR3' size='450' side='right' scene='' caption='' | ||
[[Image:Coagulation full.svg.png|thumb|450px|The coagulation cascade.]] | |||
==Introduction== | ==Introduction== | ||
'''Factor X''' is a vitamin K-dependent [http://en.wikipedia.org/wiki/Glycoprotein glycoprotein] that is synthesized in the liver. [http://en.wikipedia.org/wiki/Zymogen Zymogen] factor X circulates in plasma as a 2 chain molecule composed of a disulfide linked light chain (Mr = 16500) and heavy chain (Mr = 42,000). Factor X is activated to '''factor Xa''' by cleavage of the activation peptide. This reaction is catalyzed by [http://en.wikipedia.org/wiki/Factor_VIIa factor VIIa]-[http://en.wikipedia.org/wiki/Tissue_factor tissue factor] (extrinsic Xase complex) and [http://en.wikipedia.org/wiki/Factor_ixa factor IXa]-[http://en.wikipedia.org/wiki/Factor_viiia factor VIIIa] (intrinsic Xase complex).<ref name="Greer">Greer, John (2008). ''Wintrobe's Clinical Hematology'', p. 545-546. Lippincott Williams & Wilkins. ISBN 0781765072.</ref> | '''Factor X''' is a vitamin K-dependent [http://en.wikipedia.org/wiki/Glycoprotein glycoprotein] that is synthesized in the liver. [http://en.wikipedia.org/wiki/Zymogen Zymogen] factor X circulates in plasma as a 2 chain molecule composed of a disulfide linked light chain (Mr = 16500) and heavy chain (Mr = 42,000). Factor X is activated to '''factor Xa''' by cleavage of the activation peptide. This reaction is catalyzed by [http://en.wikipedia.org/wiki/Factor_VIIa factor VIIa]-[http://en.wikipedia.org/wiki/Tissue_factor tissue factor] (extrinsic Xase complex) and [http://en.wikipedia.org/wiki/Factor_ixa factor IXa]-[http://en.wikipedia.org/wiki/Factor_viiia factor VIIIa] (intrinsic Xase complex).<ref name="Greer">Greer, John (2008). ''Wintrobe's Clinical Hematology'', p. 545-546. Lippincott Williams & Wilkins. ISBN 0781765072.</ref> | ||
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==Structure== | ==Structure== | ||
Factor Xa is a member of the chymotrypsin-like clan within the serine protease family. Other clans within the mammalian family are the subtilisin-like and α/β-hydrolase fold serine proteases. <scene name='Factor_Xa/Transparent_-_no_inhib_evoluti/1'>Structural homology </scene>is seen in the mammalian serine protease family, and is particularly conserved in the active site geometry of the catalytic triad. The mammalian serine protease family is an example of divergent evolution from a common ancestor. <ref name="evolution">Department of Chemistry, University of Maine, Orono, ME. http://chemistry.umeche.maine.edu/CHY252/Peptidase3.html</ref>. | Factor Xa is a member of the chymotrypsin-like clan within the serine protease family. Other clans within the mammalian family are the subtilisin-like and α/β-hydrolase fold serine proteases. <scene name='Factor_Xa/Transparent_-_no_inhib_evoluti/1'>Structural homology </scene>is seen in the mammalian serine protease family, and is particularly conserved in the active site geometry of the catalytic triad. The mammalian serine protease family is an example of divergent evolution from a common ancestor. <ref name="evolution">Department of Chemistry, University of Maine, Orono, ME. http://chemistry.umeche.maine.edu/CHY252/Peptidase3.html</ref>. | ||
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==Post-Translational Modifications== | ==Post-Translational Modifications== | ||
Factor X is cleaved by factor IXa (in the intrinsic pathway), or by factor VIIa (in the extrinsic pathway) to release the activation peptide, and yield the active factor Xa. The vitamin K-dependent, enzymatic carboxylation of some glutamate residues allows the modified protein to bind calcium via the GLA domain. Zymogen human factor X has four carbohydrate-attachment sites in the activation peptide, O-glycosidic linkages are to Thr17 and Thr29, and N-glycosidic linkages are to Asn39 and Asn49. | Factor X is cleaved by factor IXa (in the intrinsic pathway), or by factor VIIa (in the extrinsic pathway) to release the activation peptide, and yield the active factor Xa. The vitamin K-dependent, enzymatic carboxylation of some glutamate residues allows the modified protein to bind calcium via the GLA domain. Zymogen human factor X has four carbohydrate-attachment sites in the activation peptide, O-glycosidic linkages are to Thr17 and Thr29, and N-glycosidic linkages are to Asn39 and Asn49. | ||
</StructureSection> | |||
__NOTOC__ | |||
==Enzyme Mechanism== | ==Enzyme Mechanism== | ||
