Two related thrombin-like enzymes present in Bothrops atrox venom

This article describes the presence of two new forms of a thrombin-like enz yme, both with apparent molecular masses of 38 kDa, in Bothrops atrox venom . Both share the ability to cleave fibrinogen into fibrin and to digest cas ein. Both present identical K-m on the substrate BApNA. Their N-terminal am ino acid sequences are identical for 26 residues, sharing 80% homology with batroxobin and flavoxobin. Two groups of monoclonal antibodies (mAbs) rais ed against the purified enzyme forms recognized different epitopes of the p utative corresponding enzymes present in B. atrox crude venom. On Western b lotting analysis of B, atrox crude venom, mAbs 5DB2C8, 5AA10 and 5CF11, but not mAbs 6CC5 and 6AD2-G5, revealed two or more protein bands ranging from 25 to 38 kDa, By immunoprecipitation assays, the 6AD2-G5 mAb was able to p recipitate protein bands of 36-38 kDa from B. atrox, B. leucurus, B, pradoi , B. moojeni, B. jararaca and B, neuwiedii crude venoms. Fibrinogen-clottin g activity was inhibited when the same venom specimens were pre-incubated w ith mAb 6AD2-G5, except for B, jararaca and B. neuwiedii.