Some properties and subcellular distribution of acyl-coenzyme A: retinol acyltransferase activity in rat testes

• Published in: Biochimica et biophysica acta Vol. 917; no. 1; pp. 24 - 32
• Main Authors: Chaudhary, Lala R., Nelson, Eldon C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 13.01.1987; Elsevier; North-Holland
• Subjects: Acyl-CoA; Acyltransferase; Acyltransferases - isolation & purification; Acyltransferases - metabolism; Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydroxylamine; Hydroxylamines - pharmacology; Kinetics; Male; Microsomes - enzymology; Rat testis; Rats; Rats, Inbred Strains; retinol acyltransferase; Retinol O-Fatty-Acyltransferase; Subcellular Fractions - enzymology; Testis - enzymology; Transferases; Acyltransferase; Rat testis; Acyl-CoA; Vertebrata; Mammalia; Cell fraction; Rat; Enzyme; Rodentia; Localization; Microsome; Testicle
• ISSN: 0005-2760; 0006-3002; 1879-145X; 1878-2434
• DOI: 10.1016/0005-2760(87)90279-7

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 μM and 30–40 μM, 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.