Retinyl ester hydrolase and the visual cycle in the chicken
eye.
Bustamante, Juan Jose, Shahed Ziari, Ruben D. Ramirez, and Andrew T.
C. Tsin.
Division of Life Sciences, The University of Texas at San Antonio,
San Antonio, Texas 78249
APStracts 2:0203R, 1995.
The ability of chicken retina and retinal pigment epithelium (RPE)
membrane to hydrolyze vitamin A esters ([9,10-3H] all-trans and 11
-cis retinyl palmitate) were studied. Hydrolytic activity within the
retina was optimal at acidic pH of 5.0 whereas in the RPE,
significant hydrolytic activity was exhibited over a broad range of
hydrogen ion concentrations. The highest rate of hydrolysis was
associated with the all-trans isomer and located within retina and
RPE membranes (apparent Vmax and Km were 770 pmol/min/mg and 45
[mu]M; 300 pmol/min/mg and 3.6 [mu]M, respectively). REH activities
for 11-cis retinyl palmitate in the retina and RPE were
correspondingly lower (apparent Vmax of 204 pmol/min/mg and Km of
18.5 [mu]M in the retina; apparent Vmax of 131 pmol/min/mg and Km of
4 [mu]M, RPE). Together with results from other laboratories, results
from the present study suggest that chicken retina contains important
enzymes to complete the visual cycle.
Received 21 December 1994; accepted in final form 12 July 1995.
APS Manuscript Number R720-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.