BASIC PROTEINASES FROM BOTHROPS-MOOJENI-(CAISSACA) VENOM .2. ISOLATION OF THE METALLOPROTEINASE MPB - COMPARISON OF THE PROTEOLYTIC ACTIVITY ON NATURAL SUBSTRATES BY MPB, MSP-1 AND MSP-2

A basic metalloproteinase active on casein was isolated from Bothrops moojeni venom by chromatography on Sephadex G-100, DEAE-Sephacel, SP-S ephadex C-50 and Sepharose 12. The enzyme, named MPB, is not hemorrhag ic and presents only traces of blood-clotting activity. On polyacrylam ide gel electrophoresis at pH 4.3, MPB presented a single and diffuse protein band. On sodium dodecyl sulfate-polyacrylamide gel electrophor esis, the enzyme presented two protein bands corresponding to mol. wts of 65,000 and 55,000, which stained with Schiff's reagent. The proteo lytic activity of MPB was inhibited by ethylenediaminetetracetate, 1,1 0-phenanthroline and dithiothreitol. The proteolytic activity of MPB a nd the serine proteinases MSP 1 and MSP 2 on natural substrates indica tes differences in hydrolytic specificity among these enzymes. All fib rinogen chains were degraded by the three proteinases, but MPB is the most active. On fibrin, the proteinases hydrolyzed only the alpha-chai n and alpha-polymer, leaving the beta-chain and gamma-dimer apparently untouched. The native type I collagen was partially hydrolyzed by the three enzymes but no digestion product was detected. On the contrary, calf and guinea-pig skin type I gelatins were readily digested by MSP 1 and MSP 2 producing different hydrolysis patterns. MPB was the leas t active proteinase on the gelatins. The digestion of fibronectin show ed an inversion in the specificity of these proteinases. MPB was the m ost active on fibronectin, while MSP 1 and MSP 2 promoted a faint, par tial hydrolysis on this protein.