Detection of a novel plasma serine protease during purification of vitaminK-dependent coagulation factors

A novel serine protease (PHBSP) was purified from human plasma by two chrom atographic steps with a final yield of 1.6 mg/l plasma, The protease consis ts of two disulfide-bridged chains of about 50 and 30 kDa with the light ch ain containing the active site of the enzyme. NH2-terminal sequence analysi s revealed identity to the deduced amino acid sequence of HGFA-like mRNA, T he activity of PHBSP is strongly dependent on Ca2+ ions and is efficiently inhibited by alpha(2)-antiplasmin and aprotinin, Possible functions of PHBS P in the hemostatic system are discussed. (C) 1999 Federation of European B iochemical Societies.