[Effect of trypsin inhibitor of a peptide-protein nature on kallikreins from human and rabbit blood stream].

The effect of three natural trypsin inhibitors--polyvalent Kunitz inhibitor (BPTI), the inhibitor from cow colostrum (CTI) and the inhibitor from soybean (SBTI)--on esterase and kininogenase action of partially purified kallikrein preparations from human and rabbit blood serum is studied. The effect of each inhibitor was estimated from Ki values. The latters show that BPTI, SBTI and CTI are strong inhibitors of both kallikreins. Ki values, as estimated from the hydrolysis rate of N-bensoyl-L-arginine ethyl ester, were found to be for human blood serum kallikrein and BPTI, SBTI and CTI 1,1-10(-9), 4,7-10(-9) and 3,6-10(-8) M respectively and for rabbit kallikrein--1,7-10(-9), 2,3-10(-8) and 2,3-10(-8) M. In the case of kallikrein catalysing more specific kininogenase reaction Ki value for complex of human serum kallikrein with BPTI was 4,8-10(-10) M, for SBTI--1,1-10(-10) M and for CTI--3,6-10(-8) M; for rabbit kallikrein--1,7-10(-9) M, 1,1-10(-9) and 2,3-10(-8) M respectively. The data obtained suggest the high sensitivity of human and rabbit serum kallikreins to the trypsin inhibitor of peptide-protein nature and a close similarity in composition of the active site for both serum kallikreins and trypsin, two spices different kininogenases--from human and rabbit serum had also similarity in molecule conformation and composition active site.