Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido 041-8611, Japan
Phospholipase A2 isozyme (PLA2 II), which showed different mobility on native PAGE from that of the PLA2 (PLA2 I) purified previously, was isolated from the pyloric ceca of the starfish Asterina pectinifera. The PLA2 II was mainly oleic acid released from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. The N-terminal amino acid sequence of the PLA2 II was SVYQF. For hydrolysis of egg yolk phosphatidylcholine, the optimum pH and temperature of the PLA2 II were at around pH 9.0 and 50°C, respectively, and the activity was enhanced by 1 mM or higher concentration of Ca2+. The PLA2 II as well as porcine pancreatic PLA2 did not show fatty acid specificity for hydrolysis of phosphatidylcholine from squid mantle muscle. The PLA2 II from the pyloric ceca of A. pectinifera, however, hydrolyzed phosphatidylcholine more effectively than phosphatidylethanolamine unlike porcine pancreatic PLA2. These characteristics of the PLA2 II were the same as those of the PLA2 I.