FIBRINOLYTIC ENZYMES FROM THE VENOMS OF AGKISTRODON CONTORTRIX AND CROTALUS-BASILISCUS-BASILISCUS - CLEAVAGE SITE-SPECIFICITY TOWARDS THE ALPHA-CHAIN OF FIBRIN

Zinc metalloproteinases with fibrinolytic activity have been isolated from the venom of Agkistrodon contortrix contortrix (fibrolase) and Crotalus basiliscus basiliscus (basiliscusfibrases 1, 2 and 3). Fibrolase cleaves the Aa-chain of fibrinogen initially at a single site: Lys(413)-Leu.(414) Basiliscusfibrases 1, 2 and 3 also cleave at this site as well as others. Since cleavage in Lys-Leu locations is not common among zinc metalloproteinases, we examined the degree to which the Lys-Leu bond determines cleavage specificity and cleavage rates for these enzymes. We employed the oxidized B-chain of insulin and the following synthetic octapeptides: InsA (Leu-Val-Glu-Ala-Leu-Tyr-Leu-Val) which includes the insulin B-chain sequence around the Ala(14)-Leu(15) bond (which is cleaved by all of the enzymes); InsK (Leu-Val-Glu-Lys-Leu-Tyr-Leu-Val) which is identical to InsA apart from the Ala(4) to Lys(4) substitution; and PA alpha (His-Thr-Glu-Lys-Leu-Val-Thr-Ser) which reproduces the sequence around the Lys(413)-Leu(414) cleavage site of the A alpha-chain of fibrinogen. Results suggest that fibrolase is better adapted for cleaving the A alpha-chain at the Lys(413)-Leu(414) locus and that cleavage specificity for the enzymes tested was not dictated by the Lys-Leu bond per se, but by the surrounding sequence.