factor V -> factor Va + factor V activation peptide (thrombin catalyst)

Stable Identifier
R-HSA-140696
Type
Reaction [transition]
Species
Homo sapiens
Compartment
ReviewStatus
5/5
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This Reactome event describes thrombin (FIIa)-catalyzed cleavage of procofactor V (FV (29–2224)) at Arg737, Arg1046 and Arg1573, producing the heterodimeric FVa composed of heavy FV (29–737) and light FV (1574–2224) chains (Brummel KE et al., 2002; Orfeo T et al., 2004; reviewed by Camire RM & Bos MHA, 2009). The inhibitory B domain is released in two fragments, FV (738–1046) and FV (1047-1573).

FV circulates in the blood as an inactive procofactor composed of the following domains: A1-A2-B-A3-C1-C2. The B domain maintains FV in its inactive state via an electrostatic interaction between its basic region (BR) and acidic region (AR) (Bos MH & Camire RM, 2012; Camire RM, 2016; Dahlbäck B et al., 2017; Ruben EA et al., 2021; Mohammed BM et al., 2024). During the amplification phase, FV is activated by proteolytic cleavage at Arg737, Arg1046, and Arg1573 catalyzed by thrombin (factor IIa), releasing the inhibitory B domain (Monkovic DD & Tracy PB, 1990; Orfeo T et al., 2004; reviewed by Camire RM & Bos MHA, 2009). The B domain of FV is cleaved sequentially (Steen M & Dahlbäck B 2002; Dahlbäck B, 2023). This process begins with proteolysis at Arg737 and Arg1046, generating partially activated FVa intermediate forms that retain the acidic region (AR) (not shown here). The final cleavage at Arg1573 completely removes the B domain, fully converting FV into its activated form, FVa, which binds FXa with high-affinity (Bunce MW et al., 2013; Bos MHA & Camire RM, 2012; Ruben EA et al., 2021; Mohammed BM et al., 2023, 2024). The FVa:FXa complex, known as the prothrombinase complex, is assembled in the (Ca²⁺)-dependent manner on the cell surface, where FVa:FXa converts prothrombin (factor II, FII) to thrombin (FIIa), creating a positive feedback loop (Mann KG et al., 1988; reviewed by Stoilova-McPhie S, 2021).

Literature References
PubMed ID Title Journal Year
14982929 The factor V activation paradox

Butenas, S, Xu, H, Orfeo, T, Nesheim, ME, Brufatto, N, Mann, KG

J Biol Chem 2004
Participants
Participates
Catalyst Activity

serine-type endopeptidase activity of activated thrombin (factor IIa) [extracellular region]

This event is regulated
Orthologous Events
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