Wax ester-synthesizing activity of lipases

The synthesis/hydrolysis of wax esters was studied in an aqueous solution u sing purified rat pancreatic lipase, porcine pancreatic carboxylester lipas e, and Pseudomonas fluorescens lipase. The equilibrium between wax ester sy nthesis and hydrolysis favored ester formation at neutral pH. The synthesiz ing activities were measured using free fatty acid or triacylglycerol as th e acyl donor and an equimolar amount of long-chain alcohol as the acyl acce ptor. When oleic acid and hexa-decanol emulsified with gum arabic were incu bated with these lipases, wax ester was synthesized, in a dose- and time-de pendent manner, and the apparent equilibrium ratio of palmityl oleate/free oleic acid was about 0.9/0.1. These lipases catalyzed the hydrolysis of pal mityl oleate emulsified with gum arabic, and the apparent equilibrium ratio of palmityl oleate/free oleic acid was also about 0.9/0.1. The apparent eq uilibrium ratio of wax ester/free fatty acid catalyzed by lipase depended o n incubation pH and fatty alcohol chain length. When equimolar amounts of t rioleoylglycerol and fatty acyl alcohol were incubated with pancreatic lipa se,carboxylester lipase, or P. fluorescens lipase, wax esters were synthesi zed,dose-dependently. These results suggest that lipases can catalyze the s ynthesis of wax eaters from free fatty acids or through degradation of tria cylglycerol in an aqueous medium.