The focus of our research is to augment current concepts and theories of retinyl ester utilization in mammalian visual systems. In particular, we propose to conduct detailed biochemical analyses of a visual system hydrolase which, despite its potential physiological significance, remains largely uncharacterized. The 11-cis-retinyl ester hydrolase catalyzes the hydrolysis of 11-cis-retinyl esters stored in the retinal pigment epithelium of the eye. Thus, we believe that it must participate in the biosynthesis of 11-cis-retinal, the visual chromophore of rhodopsin. 11-cis-retinoids in-vivo can only be synthesized in the visual system and are, therefore, not normal dietary constituents. Investigation of 11-cis-retinyl ester utilization in the visual cycle may provide information vital to our understanding of various ocular disorders characterized by reduced flow of retinoids through the visual system and hence reducing the production of visual chromophore. Only limited information is available with regard to hydrolysis of 11-cis- retinyl esters in mammalian visual systems. In contrast, a complete representation of vitamin A synthase, isomerase, and dehydrogenase is given in the literature. In fact, purification procedures have been initiated or completed on all of the enzymes which are thought to play a role in the metabolism of vitamin A in the visual cycle, with the exception of the vitamin A ester hydrolases. Ultimately, a comprehensive understanding of the metabolism of vitamin A in the visual system will be contingent upon purification and detailed biochemical characterization of visual system retinyl ester hydrolase(s), specifically, the 11-cis- retinyl ester hydrolase.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY006438-05
Application #
2160207
Study Section
Visual Sciences C Study Section (VISC)
Project Start
1986-09-30
Project End
1996-03-31
Budget Start
1994-04-01
Budget End
1995-03-31
Support Year
5
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of Texas Health Science Center San Antonio
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
800772162
City
San Antonio
State
TX
Country
United States
Zip Code
78249
Mata, N L; Tsin, A T; Chambers, J P (1992) Hydrolysis of 11-cis- and all-trans-retinyl palmitate by retinal pigment epithelium microsomes. J Biol Chem 267:9794-9
Tsin, A T; Malsbury, D W (1992) Bile salt independent retinyl ester hydrolases in the bovine eye. Brain Res Bull 28:121-5
Sanders-Sanchez, S R; Malsbury, D; Tsin, A T (1990) Comparison of retinal pigment epithelium cell preparations from the bovine eye. Experientia 46:498-500
Chambers, J P; Kumar, P; Tsin, A T et al. (1990) Partial characterization of a high affinity [Ca2+ + Mg2+]-dependent adenosinetriphosphatase from bovine retina. Exp Eye Res 50:127-34
Tsin, A T; Gentles, S N; Castillo, E A (1989) Selective utilization of serum vitamin A for visual pigment synthesis. J Exp Biol 142:207-14
Phillips, T S; Tsin, A T; Reiter, R J et al. (1989) Retinoids in the bovine pineal gland. Brain Res Bull 22:259-61
Rodriguez, K A; Tsin, A T (1989) Retinyl esters in the vertebrate neuroretina. Am J Physiol 256:R255-8
Tsin, A T; Chambers, J P (1988) Light and temperature affect retinyl ester hydrolase activity and visual pigment composition. Experientia 44:20-1
Tsin, A T; Pedrozo-Fernandez, H A; Gallas, J M et al. (1988) The fluorescence quantum yield of vitamin A2. Life Sci 43:1379-84
Tsin, A T; Flores, J M; Rodriguez, K A (1987) Visual pigments and retinoids in the Mongolian jird. Life Sci 41:2085-90