Shih T W, Shealy Y F, Strother D L, Hill D L
Drug Metab Dispos. 1986 Nov-Dec;14(6):698-702.
Certain thiol-containing compounds catalyze, in a chemical reaction, the isomerization of all-trans-retinoic acid (RA) to 13-cis-RA and of 13-cis-RA to RA. Reactions approaching equilibrium contain more RA than 13-cis-RA. Small molecules effective as catalysts are glutathione, mercaptoethanol, and L-cysteine methyl ester. L-Cysteine is not a catalyst and inhibits the reaction catalyzed by glutathione or mercaptoethanol. Apoferritin (a thiol-containing protein), native microsomes, and, to a lesser extent, boiled microsomes catalyze the reaction, but their activity is reduced or eliminated by prior incubation with iodoacetate. Other cis and trans isomeric retinoids are also substrates for this reaction; the reactions proceed more readily for the cis isomers. The thiol-catalyzed isomerization of RA and 13-cis-RA may account for the observations of both cis and trans forms of retinoids in tissues of animals after administration of either.
某些含硫醇的化合物在化学反应中催化全反式视黄酸（RA）异构化为13-顺式视黄酸（13-cis-RA）以及13-顺式视黄酸异构化为视黄酸。接近平衡的反应中视黄酸的含量比13-顺式视黄酸多。作为催化剂有效的小分子有谷胱甘肽、巯基乙醇和L-半胱氨酸甲酯。L-半胱氨酸不是催化剂，反而会抑制谷胱甘肽或巯基乙醇催化的反应。脱铁铁蛋白（一种含硫醇的蛋白质）、天然微粒体以及在较小程度上煮沸的微粒体可催化该反应，但它们的活性会因预先用碘乙酸孵育而降低或消除。其他顺式和反式异构的类视黄醇也是该反应的底物；顺式异构体的反应进行得更顺利。硫醇催化的视黄酸和13-顺式视黄酸的异构化可能解释了在给予任何一种视黄醇后，动物组织中同时出现顺式和反式视黄醇形式的现象。
