Phospholipase A of Snake Venoms I. ISOLATION AND MOLECULAR PROPERTIES OF ISOENZYMES FROM NAJA NAJA AND VIPERA

A combination of narrow range isoelectric focusing, electrophoresis on polyacrylamide gel, and gel exclusion on Sephadex reveals the presence of at least 9, possibly 11 isoenzymes of phospholipase A in Naja naja (cobra) venom. Their isoelectric points range from pH 4.60 to 5.66 and their molecular weights from 8,500 to 20,200. The most abundant form (isoelectric point = pH 4.95) has been isolated in apparently homogeneous state. All other forms have been prepared free from catalytically inactive impurities and partially or completely separated from each other. Vipera russeltii venom has been shown to contain seven isoenzymes with isoelectric points ranging from pH 4.62 to 9.90 and molecular weights from below 15,000 to 23,800. The two components responsible for most of the catalytic activity of the venom on pure phosphatides (isoelectric points = pH 9.52 and 9.90) may be isolated from crude venom in a single isoelectric focusing step in approximately 90 % homogeneous state. It has been shown that the isoenzymes of cobra venom do not arise by proteolysis or other preparative mod%cation during isolation and they do not appear to have a subunit structure. A simple and rapid assay method involving a recording pH meter and aqueous media suitable for kinetic studies on the enzyme, is described.