Esterification of retinol in lacrimal gland. Evidence for acyl-CoA:retinol acyltransferase activity. 1990

J L Ubels, and S M Huebler
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.

Vitamin A is stored in cells as long-chain fatty acyl esters of retinol. Esterification in many tissues is catalyzed in part by acyl-CoA:retinol acyltransferase (ARAT). Since the lacrimal gland contains stores of retinyl esters, it was the goal of this study to determine whether the lacrimal gland contains ARAT activity. Rabbit lacrimal gland microsomes incubated with 3H-retinol synthesized retinyl esters. The reaction rate was stimulated 30-fold in the presence of a fatty acyl-CoA generating system, producing a mixture of esters including retinyl laurate, retinyl linoleate, retinyl palmitate, and retinyl stearate as determined by reverse-phase HPLC. Retinyl palmitate was synthesized at 1944 pmole/mg protein/30 min, representing 50% of total ester synthesis, and this activity was directly proportional to microsomal protein concentration. In the presence of 180 microM 3H-retinol and 100 microM palmitoyl-CoA, retinyl palmitate was synthesized at 175-220 pmole/mg/min, and the reaction fit Michaelis-Menten kinetics as a function of retinal concentration (theoretical Vmax = 329.4 pmole/mg/min). Lauroyl CoA and stearoyl CoA, but not linoleoyl CoA, were as effective as palmitoyl CoA as substrates for the reaction. The enzyme activity was inhibited by p-chloromercuriphenyl sulfonic acid and Na-taurocholate. The data show that the lacrimal gland synthesizes retinyl esters and that the characteristics of synthesis are consistent with the presence of acyl-CoA:retinol acyltransferase in lacrimal gland.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D007765 Lacrimal Apparatus The tear-forming and tear-conducting system which includes the lacrimal glands, eyelid margins, conjunctival sac, and the tear drainage system. Lacrimal Gland,Nasolacrimal Apparatus,Conjunctival Sacs,Lacrimal Ducts,Lacrimal Punctum,Lateral Canthus,Medial Canthus,Apparatus, Lacrimal,Apparatus, Nasolacrimal,Canthus, Lateral,Canthus, Medial,Conjunctival Sac,Duct, Lacrimal,Gland, Lacrimal,Lacrimal Duct,Lacrimal Glands,Lacrimal Punctums,Punctum, Lacrimal,Sac, Conjunctival
D008861 Microsomes Artifactual vesicles formed from the endoplasmic reticulum when cells are disrupted. They are isolated by differential centrifugation and are composed of three structural features: rough vesicles, smooth vesicles, and ribosomes. Numerous enzyme activities are associated with the microsomal fraction. (Glick, Glossary of Biochemistry and Molecular Biology, 1990; from Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed) Microsome
D010171 Palmitoyl Coenzyme A A fatty acid coenzyme derivative which plays a key role in fatty acid oxidation and biosynthesis. Palmitoyl CoA,Hexadecanoyl CoA,Palmityl CoA,CoA, Hexadecanoyl,CoA, Palmitoyl,CoA, Palmityl,Coenzyme A, Palmitoyl
D011817 Rabbits A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes. Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D002851 Chromatography, High Pressure Liquid Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed. Chromatography, High Performance Liquid,Chromatography, High Speed Liquid,Chromatography, Liquid, High Pressure,HPLC,High Performance Liquid Chromatography,High-Performance Liquid Chromatography,UPLC,Ultra Performance Liquid Chromatography,Chromatography, High-Performance Liquid,High-Performance Liquid Chromatographies,Liquid Chromatography, High-Performance
D004224 Diterpenes Twenty-carbon compounds derived from MEVALONIC ACID or deoxyxylulose phosphate. Diterpene,Diterpenes, Cembrane,Diterpenes, Labdane,Diterpenoid,Labdane Diterpene,Norditerpene,Norditerpenes,Norditerpenoid,Cembranes,Diterpenoids,Labdanes,Norditerpenoids,Cembrane Diterpenes,Diterpene, Labdane,Labdane Diterpenes
D004951 Esterification The process of converting an acid into an alkyl or aryl derivative. Most frequently the process consists of the reaction of an acid with an alcohol in the presence of a trace of mineral acid as catalyst or the reaction of an acyl chloride with an alcohol. Esterification can also be accomplished by enzymatic processes. Esterifications
D000084562 Retinyl Esters A carboxylic ester of retinol formed by condensation of the hydroxy group of retinol with a carboxy group. All-Trans-Retinyl Ester,All-Trans-Retinyl Esters,Retinyl Ester,All Trans Retinyl Ester,All Trans Retinyl Esters,Ester, All-Trans-Retinyl,Ester, Retinyl
D000214 Acyl Coenzyme A S-Acyl coenzyme A. Fatty acid coenzyme A derivatives that are involved in the biosynthesis and oxidation of fatty acids as well as in ceramide formation. Acyl CoA,Fatty Acyl CoA,Long-Chain Acyl CoA,Acyl CoA, Fatty,Acyl CoA, Long-Chain,CoA, Acyl,CoA, Fatty Acyl,CoA, Long-Chain Acyl,Coenzyme A, Acyl,Long Chain Acyl CoA

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