Activation of retinoic acid by coenzyme A for the formation of ethyl retinoate.

All-trans-retinoic acid is metabolized to a less polar metabolite in rat liver microsomes. This metabolite was proven to be ethyl retinoate by cochromatography on high-performance liquid chromatography, base hydrolysis to all-trans-retinoic acid, and gas chromatography/mass spectral analysis. The formation of ethyl retinoate is a specific enzymatic process; the apparent Km for all-trans-retinoic acid is 9.8 microM. The production of ethyl retinoate is greatly stimulated by the addition of coenzyme A, suggesting the formation of a retinoic acid-coenzyme A intermediate (retinoyl-coenzyme A).