Microsomal Esterase of Rat Liver

Rat liver microsomal esterase has been purified 254-fold by a combination of solubilization in a mechanical cell homogenizer, acetone and ammonium sulfate precipitations, and hydroxylapatite column chromatography. The enzyme hydrolyzed glyceryl 1-monodecanoate at a rapid rate; the Km is 1.61 x 10-3 m. The hydrolysis rates of corresponding di- and triglycerides were one-third and one-hundredth of that of glycerol 1-monodecanoate, respectively. The enzyme showed little hydrolytic activity on long chain mono-, and di- and triglycerides. p-Nitrophenyl esters of short chain fatty acids were hydrolyzed at appreciable rates. Diethyl p-nitrophenyl phosphate, at a concentration of 1 x 10-4 m, inhibited the enzyme activity completely; thus the enzyme was tentatively classified as the B-type described by Aldridge.