[Effect of bradkinin-potentiating snake venom peptides and C-terminal pentapeptide fragment of bradkinin on carboxypeptidase N and kiniase activities of human blood serum].

Effects of bradikinin-potentiating peptides (BPP5a and BPPB), which are identical to peptides from Bothrops jararaca and Agkistrodon halys blomhoffii snake venom, and pentapeptide C-terminal bradikinin fragment on carboxypeptidase N and kinase activities in human blood serum are studied. It is found that BPP5a and BPPB at concentrations of 5-10(-4) M and 2.5-10(-4) M respectively do not inhibit the hydrolysis of hippuryl-L-lysine and hippuryl-L-argininic acid by carboxypeptidase N and at a concentration of 2-10(-3) M they do not affect the rate of the release of C-terminal arginine residue from bradikinin. BPP5a and BPPB do not inhibit the kininase activity of diluted human blood serum in vitro. Unlike BPP5a and BPPB, C-terminal pentapeptide bradikinin fragment is a competitive inhibitor of carboxypeptidase N, and it inhibits (at a concentration of 5-10(-4) M) the hydrolysis of hippuryl-L-lysine and hippuryl-L-argininic acid by 50%. It also inhibits the hydrolysis of bradikinin with diluted human blood serum. BPP5a and BPPB have an inconstant constriction effect on isolated rat uterus at concentration exceeding 4-6 orders the concentration of bradikinin. BPP5a at concentrations from 4-10(-9) to 4-10(-8) g/ml increases the sensitivity of rat uterus in 1.6--2.0 times.