Publication Date:
1987-06-26
Description:
Thirty years have elapsed since Wald and his colleagues showed that 11-cis retinal was isomerized to all-trans when rhodopsin was bleached, yet little has been understood about the reverse process that generates 11-cis retinal for rhodopsin regeneration. It is not known whether the isomerization is enzyme-mediated, whether it occurs in the pigment epithelium or in the retina, or whether retinal, retinol, or a retinyl ester is the vitamin A compound that is isomerized. Radiolabeled all-trans retinol and high-performance liquid chromatography have now been used to demonstrate the existence of an eye-specific, membrane-bound enzyme (retinol isomerase) that converts all-trans to 11-cis retinol in the dark. Retinol isomerase is concentrated in the pigment epithelium; this localization clarifies the role of this tissue in rhodopsin regeneration and explains the need to transfer all-trans retinol from the rod outer segments to the pigment epithelium during the visual cycle.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bridges, C D -- Alvarez, R A -- New York, N.Y. -- Science. 1987 Jun 26;236(4809):1678-80.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3603006" target="_blank"〉PubMed〈/a〉
Keywords:
Animals
;
Anura
;
Choroid/enzymology
;
Chromatography, High Pressure Liquid
;
Dark Adaptation
;
Hot Temperature
;
In Vitro Techniques
;
Isomerases/antagonists & inhibitors/*metabolism
;
Light
;
Liver/enzymology
;
Phenylmethylsulfonyl Fluoride/pharmacology
;
Pigment Epithelium of Eye/*enzymology
;
Rats
;
Retina/enzymology
;
Trypsin
;
Vitamin A/*metabolism
;
*cis-trans-Isomerases
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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