Purification and Properties of an Acetyl Ester Hydrolase (Acetylesterase) from Lactobacillus plantarum

Lactobacillus plantarum possesses an acetyl ester hydrolase, E C 3.1.1.6. (acetyl-esterase). The enzyme was purified from cellfree extract by ammonium sulfate precipitation, heat treatment, acetone fractionation, and ion-exchange chromatography on diethylaminoethyl-Sephadex A 50. Maximum enzyme activity was at pH 6.7 and 40C when a solution of triacetin was used as substrate. The activity of acetylesterase was not affected by dilute concentration of heavy metals such as mercury or by respiratory poisons like cyanide and azide. Higher concentration of cyanide and azide however, caused a marked inhibition. The enzyme was only slightly inhibited by specific sulfhydryl reagents. The enzyme had a strong preference for substrate in solution rather than in emulsion and preferentially hydrolyzed substrates containing acetylesters. Triglycerides were hydrolyzed at decreasing rates in the order of triacetin, tripropionin, and tributyrin.