Characteristics of a Monoacylglycerol Lipase Isolated from Pseudomonas sp. LP7315 -Hydrolysis and Synthesis of Monoglycerides

A monoacylglycerollipase (MGL) was purified from Pseudomonas sp. LP7315 by ammonium sulfate precipitation, anion-exchange chromatography, and preparative electrophoresis. The purified enzyme was homogeneous on an SDS-polyacrylamide gel with a molecular mass of 59 kDa. Its hydrolytic activity was confirmed to be specific for monoglycerides: the enzyme did not hydrolyze diand triglycerides. MGL was found to be stable even after l-h incubation at 65°C. The hydrolytic activity depended not only on temperature and pH but also on the type of monoglyceride used. MGL also catalyzed monoglyceride synthesis at 65°C in a solvent-free two-phase system, in which fatty acid droplets were dispersed in the glycerol phase with a low water content. The synthetic reaction proceeded at a constant rate for approximately 24 h and reached an equilibrium after 48 h of reaction. The initial rate of the synthetic reaction depended on several factors: the type of fatty acid used as the substrate, the amounts of fatty acid and glycerol, and the concentration of MGL in the glycerol phase. To analyze the effects of these factors, a kinetic model was developed based on the assumption that the adsorption equilibrium of MGL molecules at the interface between the two phases is the ratedetermining factor for the synthetic reaction. The model was found to yield a good approximation of the initial synthetic rate under various reaction conditions. The analysis suggests that the adsorption behavior ofMGL onto the interface had a large effect on the initial rate ofthe monoglyceride synthesis.