title: Hydrolysis of cis and trans isomers of retinyl palmitate by retinyl ester hydrolase of pig liver.
abstract: Relative retinyl ester hydrolase activities of pig liver homogenates (n = 4) toward 9,13-cis-, 13-cis-, 9-cis-, and all-trans-retinyl palmitate were 6.8 +/- 0.5 (SE), 5.7 +/- 0.5, 2.4 +/- 0.1, and 1, respectively. The range of apparent Km values for the four isomers was 142 to 268 microM, and the pH optima were 8-9 in all cases. Peak activities of retinyl ester hydrolase activities in pig liver cytosol toward 13-cis- and all-trans-retinyl palmitate were found in the 20 to 40% and in the 60 to 80% saturated ammonium sulfate (AS) fractions, respectively. By use of size-exclusion chromatography in 2 M KCl, hydrolase activity eluted at volumes corresponding to greater than 2000, 180, and 15 kDa from the 20-40% AS fraction, and at 180 kDa from the 60-80% AS fraction. On the basis of molecular size, different substrate specificities, detergent effects, and susceptibilities to inhibition by phenylmethylsulfonyl fluoride, we conclude that at least three distinct retinyl ester hydrolases are present in pig liver cytosol.
authors.affiliation: Department of Biochemistry and Biophysics, Iowa State University, Ames 50011.
authors.forename: D A
authors.initials: DA
authors.lastname: Cooper
authors.forename: J A
authors.initials: JA
authors.lastname: Olson
mesh_terms: D000645:Ammonium Sulfate; D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D011232:Chemical Precipitation; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000201:enzymology; D004224:Diterpenes; D006868:Hydrolysis; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D000084562:Retinyl Esters; D013237:Stereoisomerism; D013552:Swine; D014801:Vitamin A / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D004224:Diterpenes; D000084562:Retinyl Esters; D014801:Vitamin A; C014794:retinol palmitate; D010664:Phenylmethylsulfonyl Fluoride; D002265:Carboxylic Ester Hydrolases; C022523:retinyl esterase; D000645:Ammonium Sulfate