The interfacial pressure is an important parameter for the rate of phospholipase D catalyzed reactions in emulsion systems

Phospholipase D (PLD) is widely used for the transformation of phospholipids, which is preferably performed in aqueous-organic emulsion systems. The influence of the organic solvent on the reaction rates has been studied on the hydrolysis of phosphatidylcholine (PC) and its transesterification with glycerol by two types of PLD (cabbage and Streptomyces sp.). The initial rates determined by quantitative HPTLC show great differences in dependence on the solvent used with a similar tendency for both reactions and both PLDs. Since the polymorphism of the PC aggregates was assumed to be responsible for these effects, the critical concentration of micelle formation, the size of the aggregates, the water content of the organic phase, and the interfacial tension were determined in the different reaction systems. As result the interfacial pressure in the reaction systems influencing the package density of the PC aggregates is suggested to regulate the enzymatic activity.