Purification and characterization of a phospholipase A2 from Cerastes cerastes (horn viper) snake venom

A single phospholipase A2 has been found in Cerastes cerastes venom, purified to homogeneity by a combination of chromatographic steps involving gel filtration on Sephadex G-50 and ion-exchange chromatography on DEAE-Sephadex A-50. Its mol. wt, its amino acid composition and its partial amino acid sequence have been determined. High homologies between its sequence and those of other Viperid phospholipides A2 have been noticed. The phospholipase was non-lethal to mice up to a dose as high as 25 mg/kg by i.p. and i.v. injection. This non-toxic enzyme exhibited an acidic isoelectric point and hydrolyzed monolayers of different short chain phospholipids. Some kinetic parameters have been studied potentiometric titration (with or without Triton X-100) and the rate of catalysis seemed not to be affected by changes in the physical state of the substrate.