Studies on the Phospholipase A₂ in Pyloric Caeca of the Starfish Asterina pectinifera

Abstract

The occurrence of remarkable activity of phospholipase A₂ was found in fresh homogenate of pyloric caeca of starfish, mainly using lecithin labeled with ³H-palmitic acid at α-position as substrate. The effects of incubation time, enzyme (protein) concentration, divalent cations, and EDTA on the hydrolysis of substrate were investigated. The activity was markedly inhibited with EDTA and was dependent on divalent cations such as Ca⁺⁺. Sodium deoxycholate and certain organic solvents such as benzene, diethylether etc. also activated the enzyme. The optimal pH was about 8. The occurrence of low activity of lyso-phospholipase was also found in fresh homogenate but little lipase activity was detected.