Phospholipase A of sea snake Laticauda semifasciata venom. Isolation and properties of novel forms lacking tryptophan

Abstract

The venom gland extracts of the sea snake Laticauda semifasciata contained at least four forms of phospholipase A separable on a CM-cellulose column. They were designated as phospholipases A I-IV in the order of elution from the column. Phospholipases A I, III, and IV were isolated in a homogeneous state. They were similar to one another in amino acid composition and molecular weight (14,000) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Phospholipase A I contained one tryptophan residue. whereas III and IV did not. Although all these forms had the same A2-type positional specificity, they were classified into two groups (I, and III and IV) on the basis of enzymic properties. Phospholipase A I had a higher specific activity and showed normal kinetics, whereas III and IV had approximately one-tenth of the specific activity of I and showed biphasic kinetics due to their activation by the reaction products. Phospholipase A I, the major form, seems to be identical with phospholipase A reported previously (Tu, A.T., Passey, R.B., & Toom, P.M. (1970) Arch. Biochem. Biophys. 140, 96-106), whereas the other two, III and IV, are new. Phospholipase A I became more like III and IV in enzymic properties on modification with N-bromosuccinimide.