Metalloproteinase with factor X activating and fibrinogenolytic activities from Vipera berus berus venom

We have previously shown that Vipera berus berus venom contains several factor X activating enzymes. In the present study we have investigated one of them. The enzyme was separated from venom by gel filtration on Sephadex G-100 superfine and chromatography on agarose HPS-7 and phenyl-agarose. The enzyme is a glycosylated metalloproteinase containing hexoses, hexosamines and neuraminic acid. The purified factor X activating enzyme consists of two equal chains (59 kDa). The specificity studies have shown that enzyme is nonspecific factor X activating proteinase hydrolysing also proteins such as azocasein, gelatin and fibrinogen. The enzyme hydrolyses oxidized insulin B-chain at the positions Ala¹⁴–Leu¹⁵ and Tyr¹⁶–Leu¹⁷ but it is inactive on fibrin, plasminogen and prothrombin. We used 8–10 amino acid residues containing peptides, which reproduce the sequence around the cleavage sites in factor X, factor IX and fibrinogen, as potential substrates for enzyme. Cleavage products of peptide hydrolysis were determined by MALDI-TOF MS. The peptide Asn–Asn–Leu–Thr–Arg–Ile–Val–Gly–Gly—factor X fragment was cleaved by enzyme at positions Leu³–Thr⁴ and Arg⁵–Ile⁶. The fibrinogen peptide fragment Glu–Tyr–His–Thr–Glu–Lys–Leu–Val–Thr–Ser was hydrolysed at position Lys⁶–Leu⁷.