An all-trans-retinyl ester is a retinyl ester whose retinyl-chain double bonds have trans geometry. The prefix specifies that part of the molecule; the attached acyl group can still vary. A sample described only by this class name is consequently not a completely specified individual compound.[ref]
All-trans-retinyl ester in ChEBI. CHEBI:63410, Definition and generic structure
Two independent structural choices are involved. Changing the attached acyl group can alter the molecular formula while leaving retinyl-chain geometry unchanged. Changing one retinyl double bond from trans to cis instead changes the geometry without necessarily changing the molecular formula. Esterification and cis-trans isomerism must therefore be distinguished.
The distinction has a concrete role in the visual cycle. A 2005 expression experiment showed that RPE65 converts an all-trans-retinyl ester substrate into 11-cis-retinol, provided the cells also expressed the substrate-supplying lecithin retinol acyltransferase.[ref]
RPE65 is the isomerohydrolase in the retinoid visual cycle by Gennadiy Moiseyev and others. Abstract, supplied ester substrate and 11-cis product
The observed product differs in both ester status and retinyl geometry. Measuring only total retinoid would conceal those chemically important changes. Articles by others on the same topic
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