coagulation factor XIIa

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Function

serine protease, proteolytically activates factor XI & prekallikrein
prekallikrein is cleaved by factor XII to form kallikrein, which then cleaves factor XII first to alpha-factor XIIa & then trypsin cleaves it to beta-factor XIIa
alpha-factor XIIa activates factor XI to factor XIa
selective cleavage of Arg-|-Ile bonds in factor VII to form factor VIIa & factor XI to form factor XIa
factor XII is activated by kallikrein in alpha-factor XIIa, which is then further converted by trypsin into beta-factor XIIa
alpha-factor XIIa is composed of the NH2-terminal heavy chain (coagulation factor XIIa heavy chain) & the COOH-terminal light chain (coagulation factor XIIa light chain), connected by a disulfide bond
beta-factor XIIa is composed of 2 chains linked by a disulfide bond, a light chain (beta-factor XIIa part 2), corresponding to the COOH-terminal light chain (coagulation factor XIIa light chain) & a nonapeptide (beta-factor XIIa part 1)