Editing Factor X (section)

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{{Short description|Mammalian protein found in Homo sapiens}}
{{Other uses}}
{{Infobox_gene}}

'''Coagulation factor X''' ({{EC number|3.4.21.6}}),  or '''Stuart factor''', is an [[enzyme]] of the [[coagulation cascade]], encoded in humans by ''F10'' gene.<ref name="Medline2024">{{cite web |title=F10 gene: MedlinePlus Genetics |url=https://medlineplus.gov/genetics/gene/f10/ |website=medlineplus.gov |language=en}}</ref> It is a [[serine endopeptidase]] (protease group S1, [[PA clan]]). Factor X is synthesized in the [[liver]] and requires [[vitamin K]] for its synthesis.

Factor X is activated, by hydrolysis, into '''factor Xa''' by both [[factor IX]] with its cofactor, [[factor VIII]] in a complex known as [[Tenase|intrinsic pathway]]; and [[factor VII]] with its cofactor, [[tissue factor]] in a complex known as [[Tenase|extrinsic pathway]].<ref name="Camire">{{cite journal | vauthors = Camire RM | title = Blood coagulation factor X: molecular biology, inherited disease, and engineered therapeutics | journal = Journal of Thrombosis and Thrombolysis | volume = 52 | issue = 2 | pages = 383–390 | date = August 2021 | pmid = 33886037 | pmc = 8531165 | doi = 10.1007/s11239-021-02456-w }}</ref> It is therefore the first member of the ''final common pathway'' or ''thrombin pathway''.

It acts by cleaving [[prothrombin]] in two places (an [[arginine|Arg]]-[[threonine|Thr]] and then an [[arginine|Arg]]-[[isoleucine|Ile]] bond), which yields the active [[thrombin]]. This process is optimized when factor Xa is complexed with activated [[factor V|co-factor V]] in the [[prothrombinase]] complex.

Factor Xa is inactivated by [[protein Z-dependent protease inhibitor]] (ZPI), a [[serine protease inhibitor]] (serpin). The affinity of this protein for factor Xa is increased 1000-fold by the presence of [[protein Z]], while it does not require protein Z for inactivation of [[factor XI]]. Defects in protein Z lead to increased factor Xa activity and a propensity for thrombosis. The half life of factor X is 40–45 hours.