PURIFICATION AND PRIMARY STRUCTURE OF A MYOTOXIC LYSINE-49 PHOSPHOLIPASE A(2) WITH LOW LIPOLYTIC-ACTIVITY FROM TRIMERESURUS-GRAMINEUS VENOM

Four acidic phospholipase A(2) (PLA(2)) isozymes named PLA(2)-I, II, III and IV have previously been isolated from Trimeresurus gramineus (green habu snake) venom and sequenced [Oda et al. (1991) Toxicon 29, 157; Fukagawa et al, (1992) Toxicon 30, 1131; Fukagawa et al, (1993) Toxicon 31, 957]. They contain aspartate-49 which is known to bind Ca2+, essential for catalysis. In the present study, a basic PLA(2) named PLA(2)-V containing lysine-49 was newly isolated from the same snake venom. Its isoelectric point was 9.4 and considerably higher than those (c. 4.5) of PLA(2)-I-IV. PLA(2)-V was 1.1% as active as PLA(2)-I toward egg-yolk emulsion but exhibited strong myotoxicity. The amino acid sequence of PLA(2)-V was determined by sequencing the S-carboxamidomethylated derivative and its peptide fragments produced by enzymatic (clostripain, chymotrypsin, Achromobacter protease I and Staphylococcus aureus V8 protease) cleavages, PLA(2)-V consists of 122 amino acid residues and is highly homologous (72-78%) to Lys-49 PLA(2)s so far isolated from Viperidae snake venoms but less homologous (52%) to PLA(2)-I. The presence of Asn-28, which is characteristic of Lys-49 PLA(2)s, was confirmed.