title: Some properties and subcellular distribution of acyl-coenzyme A: retinol acyltransferase activity in rat testes.
abstract: The present study was conducted to examine esterification of retinol by testicular microsomes. The microsomes were isolated from rat testes and were incubated under varying assay conditions with [3H]retinol. [3H]Retinylpalmitate was identified by reversed-phase high-performance liquid chromatography as an esterified product. The rate of esterification was increased by the addition of a fatty acyl-CoA. Coenzyme A esters of oleic, palmitic and stearic acids were equally effective substrates for retinol esterification. A 17-fold increase was observed in the presence of palmitoyl-CoA when microsomes had been pretreated with hydroxylamine, a reagent that reacts with coenzyme A thioesters to form hydroxamic acids. The esterifying activity was stimulated by the addition of dithiothreitol (4 mM) and fatty acid-free bovine serum albumin (1 mg/ml). The optimal concentrations for retinol and palmitoyl-CoA were 40 microM and 30-40 microM, respectively. The enzyme activity was inhibited by p-hydroxymercuribenzoate, sodium taurocholate and 5,5'-dithiobis-(2-nitrobenzoic acid), but not by EDTA. The enzyme activity was highest in microsomes (36%). However, some activity was present in mitochondria (29%). These results clearly show the presence of a fatty acyl-CoA: retinol acyltransferase that catalyzes the esterification of retinol in rat testes.
mesh_terms: D000217:Acyltransferases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D051142:Retinol O-Fatty-Acyltransferase; D013347:Subcellular Fractions / Q000201:enzymology; D013737:Testis / Q000201:enzymology*
chemical_list: D006898:Hydroxylamines; D019811:Hydroxylamine; D000217:Acyltransferases; D051142:Retinol O-Fatty-Acyltransferase