Biochemical and physiological studies on a kallikrein-like enzyme from the venom of Crotalus viridis viridis (Prairie rattlesnake)

Abstract

A kallikrein-like enzyme was isolated from Crotalus viridis viridis (Prairie rattlesnake) venom by Sephadex G-50, DEAE-Sephacel and heparin-Sepharose CL-6B column chromatography. The purified enzyme has a molecular mass of 32 kDa and an isoelectric point of 5.4. The enzyme catalyzed the hydrolysis of arginine esters, kallikrein substrates ProPheArgMCA and ZPheArgMCA. The specificity of the enzyme's substrate requirement is demonstrated by the fact that no proteolytic activity was detected against either dimethyl casein or fibrinogen. The enzyme also cleaves kininogen analogs to release bradykinin. Although the enzyme induced contraction of the isolated rat uterus directly at high concentrations, more forceful contractions resulted when the reaction mixture of the enzyme and bovine plasma was applied to the uterus. The reaction mixture of 5 · 10 −11 M of the enzyme and plasma caused contractions equal to that of 10 −9 M of bradykinin. Additionally the enzyme demonstrated capillary permeability-increasing activity and hypotensive activity on the anaesthetized rat, suggesting that the enzyme releases the dilator of the wall of capillaries from plasma. Uterine contraction, capillary permeability-increasing activity and arginine esterolytic activity were inhibited by diisopropyl fluorophosphate, indicating that the serine hydroxyl group is essential for enzymatic and biological activities. It was demonstrated that the NH 2-terminal region of the enzyme has significant similarities in sequence with kallikrein-like enzymes from other snake venoms and porcine pancreatic kallikrein.