1994 Volume 115 Issue 4 Pages 743-751
Three Streptoverticillium anticoagulants, SAC I, II, and III, which strongly inhibit human intrinsic blood coagulation, were each isolated in a homogeneous form from a culture fluid of Streptoverticillium cinnamoneum subsp. cinnamoneum IFO 12852. SAC I, II, and III are simple proteins with molecular weights of around 12, 000, and with isoelectric points of 9.7, 9.7, and 9.9, respectively. Their amino acid compositions are similar and each SAC possesses two disulfide bonds. The COOH-terminal residue of each of these proteins is phenylalanine. Together with the similarity of their protein chemical properties, the results of NH2-terminal amino acid sequence analysis of these SAC proteins strongly suggested that the deletion of Ser-Leu and Ser-Leu-Tyr from the NH2-terminus of SAC I (Ser-Leu-Tyr-Ala-Pro-...) results in the generation of SAC II and III, respectively. The amount of each SAC necessary to double the partial thromboplastin time was around 5 μg/ml. SAC I inhibited activated human factor XII and human plasma kallikrein. It also inhibited, but to a lesser extent, activated factor X. The inhibition constants (K1) of SAC I toward activated factor XII and plasma kallikrein were 5.3×10-8 and 7.2×10-9 M, respectively. The SACs also inhibited some microbial serine proteases such as subtilisin Carlsberg and, to a lesser extent, mammalian serine proteases including bovine trypsin and α-chymotrypsin. Of these three inhibitors, only SAC I inhibited metalloproteases such as thermolysin in addition to these serine proteases.
