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 phospholipid s, which is preferably performed in aqueous-organic emulsion systems. The i nfluence of the organic solvent on the reaction rates has been studied on t he hydrolysis of phosphatidylcholine (PC) and its transesterification with glycerol by two types of PLD (cabbage and Streptomyces sp.). The initial Fa tes determined by quantitative HPTLC show great differences in dependence o n 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 si te of the aggregates, the water content of the organic phase, and the inter facial tension were determined in the different reaction systems. As result the interfacial pressure in the reaction systems influencing the package d ensity of the PC aggregates is suggested to regulate the enzymatic activity . (C) 1999 Elsevier Science B.V. All rights reserved.