A Novel Nonhemorragic Protease from the African Puff Adder ( Bitis Arietans ) Venom

A nonhemorrhagic proteinase B‐20 from the venom of Bitis arietans has been purified to apparent electrophoretic homogeneity by chromatography on Sephadex G–100, Q‐Sepharose, and CM‐cellulose. It has a molecular weight of 20 k Da as determined by size exclusion chromatography on Sephadex G‐100 and migrated as a single 20‐k Da band on SDS polyacrylamide. It has an optimum pH of 6–8 and is inactive at pH 4.0. EDTA and 1,10‐phenanthroline strongly inhibited the enzyme suggesting it is a metalloenzyme. Also it is inhibited by antipain but is unaffected by trasylol, antitrypsin, and pepsptatin. Colombin, an identified active component of Aristolochia albida used in the treatment of snake poisoning, did not inhibit the protease activity. It lost over 90% of its activity in the presence of 0.5 μM Hg 2+ but the inhibition was completely blocked in the presence of 10 μM mercaptoethanol implicating sulfyhydryl groups in the catalytic entity of the protein. The activity was also inhibited competitively by glutathione and cysteine with inhibition binding constants K i of 240 and 40 μM, respectively. The enzyme is unaffected by several divalent cations but activated by 1 mM Fe 3+ . It had a prolyl endopeptidase and thermolysin‐like activity. The enzyme displayed a fast acting α‐fibrinolytic and delayed γ‐fibrinolytic activity when tested on human fibrinogen. The relevance of these findings is discussed © 2001 John Wiley & Sons, Inc. J Biochem Mol Toxicol 15:215–220, 2001