173 - Venom metalloproteinases of Agkistrodon contortrix laticinctus

Abstract

Publisher Summary This chapter discusses the structural chemistry and the biological aspects of venom metalloproteinases of agkistrodon contortrix laticinctus. Agkistrodon contortrix laticinctus hemorrhagic toxin I (ACLH) is a metalloprotease isolated from the venom of Agkistrodon contortrix laticinctus species having a relative molecular mass of about 29,000. The predicted sequences for both proteins have the same pattern of domain organization, which includes very conserved proenzyme region with a signal peptide for secretory proteins and a catalytic domain with the zinc-binding motif. The third isolated clone ACLD codes for a class PHI metalloproteinase having disintegrin and cysteine-rich domains in addition to the catalytic domain. It codes for a zymogen form of 620 amino acids and a mature protein of 431 residues. The mature protein has the highly conserved zinc-binding motif of the reprolysin protein family as also found in ACLF and ACLH. The proteolytic activity of ACLH was completely inhibited by 5 mM EDTA. ACL hemorrhagic toxin I was able to completely hydrolyze the α chain of fibrinogen in about 5 minutes. The β chain of fibrinogen was also hydrolyzed but at a slower rate. The y chain was resistant to hydrolysis even after prolonged incubation.