The hydrolysis of phosphatidylcholine by phospholipase A₂ in microemulsion as microreactor

Phospholipase A₂ (PLA₂) was used to hydrolyze phosphatidylcholine (PC) in microemulsions. Phase diagrams were constructed for mixtures of alcohols (C₂-C₆), medium chain triglycerides (tricaprylin (TC)) or vegetable oils, PC and water, and areas corresponding to isotropic systems were identified. The PC hydrolysis was carried out with high yields at various PC/(TC+alcohol) compositions within the areas of isotropic systems at increasing amounts of solubilized water. The initial reaction rates depended on the aggregation state of the PC (size and nature of microemulsion structures), as well as on temperature and mode of calcium addition. At low enzyme concentrations, hydrolysis was preceded by a `lag phase' followed by an abrupt increase in rate. By contrast, no latency was observed at higher PLA<sub>2</sub>/PC ratios and the rate was significantly higher. The easy access of the enzyme to the substrate in the curved phospholipid-containing microemulsion particles facilitates activation of the enzyme and `pushes' the reaction to completion. Hence, these microemulsions can serve as microreactors for high yield enzymatic hydrolysis.