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.
