Distribution of 11-cis LRAT, 11-cis RD and 11-cis REH in bovine retinal pigment epithelium membranes.
Our recent finding of the co-localization of 11-cis retinyl esters and 11-cis retinyl ester hydrolase (11-cis REH) activity in bovine retinal pigment epithelium (RPE) plasma membrane (PM) has led us to explore the possibility that the PM may provide 11-cis retinal for rhodopsin regeneration. In the RPE, visual chromophore is synthesized via a membrane associated 11-cis retinol dehydrogenase (11-cis RD). Accordingly, bovine RPE membranes enriched with either endoplasmic reticulum (ER) or plasma membrane (PM) enzyme markers were prepared and assayed for visual cycle enzyme activities. Pronounced 11-cis RD activity was associated with both ER- and PM-enriched membrane fractions. In contrast, 11-cis REH activity was mostly recovered in PM-enriched fractions while LRAT activity was found only in ER-enriched membranes. The finding that both 11-cis retinol and 11-cis retinal can be produced at the PM of the bovine RPE strongly suggests that 11-cis retinyl esters at this subcellular locale serve as a precursor of visual chromophore for pigment regeneration.
Division of Life Sciences, The University of Texas at San Antonio, 6900 North Loop, 1604 West San Antonio, San Antonio, TX 78249, USA.
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D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D002417:Cattle; D010857:Pigment Epithelium of Eye / Q000201:enzymology* / Q000648:ultrastructure; D012172:Retinaldehyde / Q000378:metabolism; D014801:Vitamin A / Q000378:metabolism*
D014801:Vitamin A; D000429:Alcohol Oxidoreductases; C022520:retinol dehydrogenase; D002265:Carboxylic Ester Hydrolases; C022523:retinyl esterase; D012172:Retinaldehyde