Hiroshi KIHARA,** * Chun-Chang CHANG,****

Phospholipase A, was purified to homogeneity from the venom of Trimeresurus gramineus (the Green Habu snake) via three steps consisting of Sephadex G-75, DEAE-cellulose, and DEAE-Toyopearl 650M column chromatographies. Molec-ular weight determinations showed that the enzyme consists of a single polypeptide chain with a molecular weight of approximately 14,000. The isoelectric point was 4.5. The enzyme is characterized by high contents of acidic amino acids, glycine, and half-cystine. Calcium ion was essential for eliciting activity. The enzyme was inactivated by alkylation of a single histidine residue with /vbromophenacyl bromide following pseudo first-order kinetics, and the rate of the inactivation was depressed in the presence of Ca l +. The N-terminal sequence of this enzyme deter-mined to the 40th residue was found to be highly homologous to that of Trimeresurus okinavensis phospholipase A, but not to that of Trimeresurus flavoviridis phospho-lipase A,. The phenylalanine residue at the 27th position of T. gramineus phos-pholipase A2 is noteworthy because all other phospholipases A,, with only two exceptions, contain a tyrosine residue at this position. Phospholipase At [EC 3.1.1.4] catalyzes the hy- choline. Calcium ion is required for the catalysis, drolysis of the /?-ester linkage of phosphatidylcho- Approximately 40 phospholipases A, were isolated line to produce a fatty acid and lysophosphatidyl- from mammalian pancreas, snake venoms, and bee 1 To whom correspondence should be addressed