Isomerization of all-trans-retinoids to 11-cis-retinoids in vitro.
The key biochemical process of the vertebrate visual cycle required for rhodopsin regeneration, 11-cis-retinoid production from all-trans-retinoids, is shown to occur in vitro. A 600 X g supernatant from a frog retina/pigment epithelium homogenate transforms added all-trans-[3H]retinol, in a time-dependent fashion, to a mixture of 11-cis-retinol, 11-cis-retinal, and 11-cis-retinyl palmitate. 13-cis-Retinoids are formed in only minor amounts by nonspecific processes. Studies using washed particulate fractions of the 600 X g supernatant indicate that all-trans-[3H]retinol is isomerized to 11-cis-retinoids much more effectively than is all-trans-[3H]retinal or all-trans-[3H]retinyl palmitate. The 11-cis-retinoid biosynthetic activity is heat-labile, sedimentable by high-speed centrifugation, and largely found in the pigment epithelium rather than in the neural retina.
D000818:Animals; D003624:Darkness; D004848:Epithelium / Q000378:metabolism; D007700:Kinetics; D008027:Light; D011894:Rana pipiens; D012160:Retina / Q000378:metabolism*; D012176:Retinoids / Q000378:metabolism*; D013237:Stereoisomerism; D014316:Tritium; D014801:Vitamin A / Q000378:metabolism
D012176:Retinoids; D014316:Tritium; D014801:Vitamin A