Enzymic Deacylation of Lipids in Plants. The Effects of Free Fatty Acids on the Hydrolysis of Phospholipids by the Lipolytic Acyl Hydrolase of Potato Tubers

1 Deacylation of phosphatidylcholine by the lipolytic acyl hydrolase enzyme in homogenates of potato tubers was stimulated by endogenous free fatty acids in the homogenates. 2 Partially purified enzyme preparations were inactive in the absence of surface active agents. 3 The fatty acid-stimulated enzymic deacylation of phosphatidylcholine showed a pH optimum between 5.5 and 6.0 and was reversed by bovine serum albumin. 4 Free fatty acids were more effective than other lipids and surface active compounds studied. 5 Long-chain cis-unsaturated fatty acids were most effective. 6 Enzymic hydrolysis of phosphatidylethanolamine showed a similar stimulation by free fatty acids but hydrolysis of lyso-phosphatidylcholine, phosphatidylglycerol, phosphatidic acid, galactolipids or monoglycerides was not stimulated. 7 Similar stimulation by linoleic acid of the enzymic deacylation of membrane-bound phospholipid was observed and found to be prevented by bovine serum albumin. 8 Electron microscope studies suggested that free fatty acids had a marked effect on the physical state of phosphatidylcholine in aqueous dispersions.