INFLUENCE OF ACYL CHAIN COMPOSITION ON THE DEGRADATION OF PHOSPHATIDYLCHOLINE BY PHOSPHOLIPASE-D IN CARNATION MICROSOMAL-MEMBRANES

Microsomal membranes isolated from the petals of senescing carnation flowers degrade radiolabelled phosphatidylcholine into phosphatidic acid, diacylglycerol, free fatty acids and fatty acid oxidation products. A comparison of the rates of degradation for various molecular species of phosphatidylcholine has indicated that highly perturbing molecular species are preferentially degraded. Two lines of evidence indicate that phosphatidylcholine is acted upon initially by phospholipase D. First, all of the radiolabelled water soluble products released from choline-labelled phosphatidylcholine are recovered as choline. Second, the temporal patterns in which radiolabelled degradation products are formed support the contention that phosphatidylcholine is degraded by phospholipase D. The data have been interpreted as indicating that the differences in rates of degradation for various molecular species of phosphatidylcholine reflect discrimination of molecular species by phospholipase D and a preference of the enzyme for highly perturbing molecular species. This molecular species preference is exhibited by young and senescent microsomal membranes and also by membranes that have been partially solubilized with detergent. © 1990 Oxford University Press.