POLYMERIZABLE PHOSPHATIDYLCHOLINES - IMPORTANCE OF PHOSPHOLIPID MOTIONS FOR OPTIMUM PHOSPHOLIPASE-A2 AND PHOSPHOLIPASE-C ACTIVITY

Cross-linkable short-chain phosphatidylcholines with thiols at the cha in terminus have been synthesized and characterized. These micelle-for ming species were used to investigate two water-soluble phospholipases . When reduced, the thiol lipids were excellent substrates for phospho lipase A2. Once cross-linked, they became extremely poor substrates. T his is consistent with a mechanism in which a key step is the partial extraction of the substrate phosphatidylcholine from an aggregate. In contrast, phospholipase C activity was slightly enhanced if the produc t diglyceride was tethered to the aggregate through disulfide formatio n. For this enzyme such a kinetic effect is consistent with the hydrop hobic diglyceride biasing the enzyme to the interface.