11-cis-acyl-coa:retinol O-acyltransferase Activity in the Primary Culture of Chicken Muller Cells.
From: Department of Biology, University of Texas at San Antonio, San Antonio, Texas 78249, USA.
Biochemistry
- Publish Date: Oct 2006
- ISSN: 0006-2960
- Volume: 45
- Issue: 40
- Pages: 12265-73
- Medium: Print
- Language: English
- Citation (JAMA): Muniz Alberto, Villazana-Espinoza Elia T, Thackeray Bridget, et al. 11-cis-acyl-coa:retinol O-acyltransferase Activity in the Primary Culture of Chicken Muller Cells.. Biochemistry Oct 2006;45:12265-73
Abstract
A novel retinoid cycle has recently been identified in the cone-dominated chicken retina, and this cone cycle accumulates 11-cis-retinyl esters upon light adaptation. The purpose of this study is to investigate how 11-cis-retinyl esters are formed in the retina. Primary cultures of chicken Muller cells and cell membrane were incubated with all-trans- or 11-cis-retinol to study retinyl ester synthesis. In Muller cells, esterification of 11-cis-retinol was four times greater than esterification of all-trans-retinol. In the presence of palmitoyl-CoA and CRALBP, Muller cell membranes synthesized 11-cis-retinyl ester from 11-cis-retinol at a rate which was 20-fold higher than that of all-trans-retinyl ester. In the absence of CRALBP, 11-cis-retinyl ester synthesis was greatly reduced (by 7-fold). In the absence of palmitoyl-CoA, retinyl ester synthesis was not observed. Muller cell membranes incubated with radiolabeled palmitoyl-CoA resulted in the transfer of the labeled acyl group to retinol. This acyl transfer was greatly reduced in the presence of progesterone, a known ARAT inhibitor. 11-cis-ARAT activity remained unchanged when assayed in the presence of all-trans-retinol, suggesting a distinct catalytic activity from that of all-trans-ARAT. Apparent kinetic rates for 11-cis-ARAT were 0.135 nmol min(-)(1) mg(-)(1) (V(max)) and 11.25 microM (K(M)) and for all-trans-ARAT were 0.0065 nmol min(-)(1) mg(-)(1) (V(max)) and 28.88 microM (K(M)). Our data indicate that Muller cells in the chicken retina possess 11-cis-ARAT activity, thus providing an explanation for the accumulation of 11-cis-retinyl esters in the cone cycle.
Mesh Headings (Keywords): Animals, Cells, Cultured, Chickens, Isomerism, Kinetics, Palmitoyl Coenzyme A, Progesterone, Retina, Retinol O-Fatty-Acyltransferase
Check for Full Text / PubMed Unique Identifier (PMID): 17014079
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