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The catalytic activity of extracellular phospholipase A2 was studied in low polarity solvents where hydrolytic enzymes have been demonstrated to catalyze synthesis reactions. It was demonstrated that extracellular phospholipase A2 can catalyze the esterification of lysophosphatidylcholine with oleic acid. Up to 6.5% of lysophosphatidylcholine can be esterified into phosphatidylcholine. This activity requires a preincubation of the enzyme in a pH 9 aqueous solution containing calcium, before the incubation in the non-aqueous solvent. No transfer of fatty acid between a phospholipid and a lysophospholipid or between two phospholipids was observed. These results may be useful in understanding the function of the membrane phospholipase A2 which may catalyze acylation or deacylation depending on the local physico-chemical environment.

Unusual reactions of interesterification and synthesis catalyzed by Candida cylindracea lipase have been tested in reverse microemulsions. The microemulsions used are made of fatty acids or triglycerides, the enzyme dissolved in a very low water quantity, Brij 35 used as surfactant and an alcoholic cosurfactant. In such a system, fats and alcohols are both the substrates of the enzyme and the microemulsion components. Incidentally, non specific Candida cylindracea lipase does not catalyze interesterification of short chain triglycerides, revealing a specificity for the chain length. Interesterification reactions tested in the presence of a given water quantity but with varying water activities show that it is the water activity and not the water quantity which is a fundamental parameter of the system. The effect of the surfactant (Brij 35) on the interesterification reaction is studied. Heptyl-oleate synthesis catalyzed by non-specific lipase is obtained in microemulsions at a 98% yield. Synthesis of glycerol esters is also tested in monophasic medium and mono and diglycerides are obtained.