Activated protein C cleaves factor Va to factor Vi intermediate form

Activated protein C cleaves peptide bonds in activated factor V (factor Va), converting it to an inactive form (factor Vi). APC proteolysis involves cleavage of the factor Va heavy chain at Arg-334 (306 if signal peptide is not included) and Arg-534 (506 with no signal peptide) (Nicolaes et al. 1985). Most factor Va molecules are initially cleaved at Arg-534, yielding a partially active intermediate, followed by complete inactivation through cleavage at Arg-334 (Kalafatis et al. 1994). Factor Xa inhibits Arg-534 cleavage but this effect is mitigated by Protein S (Norstrom et al. 2006). A mutation of the APC cleavage sites in Fv at Arg-534Gln a.k.a. FVLeiden is the most common identifiable hereditary risk factor for venous thrombosis among Caucasians (Camire 2011).

活化蛋白C能够切断活化因子V（因子Va）的肽键，将其转化为无活性形式（因子Vi）。APC的蛋白酶解过程涉及对因子Va重链在Arg-334（若不包括信号肽则为306）和Arg-534（若无信号肽则为506）处进行切割（Nicolaes等人，1985年）。大多数因子Va分子最初在Arg-534处被切割，从而生成一种部分活性的中间产物，随后通过在Arg-334处进行切割实现完全失活（Kalafatis等人，1994年）。Xa因子能够抑制Arg-534的切割，但这一效应被蛋白S所缓解（Norstrom等人，2006年）。位于Fv的APC切割位点Arg-534Gln，即FVLeiden突变，是白种人中常见的、可识别的遗传性静脉血栓形成风险因素（Camire，2011年）。