Isolation and structural characterization of a new fibrin(ogen)olytic metalloproteinase from Bothrops moojeni snake venom

A proteinase, named BmooMPα-I, from the venom of Bothrops moojeni, was purified by DEAE-Sephacel, Sephadex G-75 and heparin-agarose column chromatography. The enzyme was purified to homogeneity as judged by its migration profile in SDS–PAGE stained with coomassie blue, and showed a molecular mass of about 24.5 kDa. Its complete cDNA was obtained by RT-PCR and the 615 bp codified for a mature protein of 205 amino acid residues. The multiple alignment of its deduced amino acid sequence and those of other snake venom metalloproteinases showed a high structural similarly, mainly among class P-IB proteases. The enzyme cleaves the Aα-chain of fibrinogen first, followed by the Bβ-chain, and shows no effects on the γ-chain. On fibrin, the enzyme hydrolyzed only the β-chain, leaving the γ-dimer apparently untouched. It was devoid of phospholipase A2, hemorrhagic and thrombin-like activities. Like many venom enzymes, it is stable at pH values between 4 and 10 and stable at 70 °C for 15 min. The inhibitory effects of EDTA on the fibrinogenolytic activity suggest that BmooMPα-I is a metalloproteinase and inhibition by β-mercaptoethanol revealed the important role of the disulfide bonds in the stabilization of the native structure. Aprotinin and benzamidine, specific serine proteinase inhibitors, had no effect on BmooMPα-I activity. Since the BmooMPα-I enzyme was found to cause defibrinogenation when administered i.p. on mice, it is expected that it may be of medical interest as a therapeutic agent in the treatment and prevention of arterial thrombosis.