title: Retinol dehydrogenases: membrane-bound enzymes for the visual function.
abstract: Retinoid metabolism is important for many physiological functions, such as differenciation, growth, and vision. In the visual context, after the absorption of light in rod photoreceptors by the visual pigment rhodopsin, 11-cis retinal is isomerized to all-trans retinal. This retinoid subsequently undergoes a series of modifications during the visual cycle through a cascade of reactions occurring in photoreceptors and in the retinal pigment epithelium. Retinol dehydrogenases (RDHs) are enzymes responsible for crucial steps of this visual cycle. They belong to a large family of proteins designated as short-chain dehydrogenases/reductases. The structure of these RDHs has been predicted using modern bioinformatics tools, which allowed to propose models with similar structures including a common Rossman fold. These enzymes undergo oxidoreduction reactions, whose direction is dictated by the preference and concentration of their individual cofactor (NAD(H)/NADP(H)). This review presents the current state of knowledge on functional and structural features of RDHs involved in the visual cycle as well as knockout models. RDHs are described as integral or peripheral enzymes. A topology model of the membrane binding of these RDHs via their N- and (or) C-terminal domain has been proposed on the basis of their individual properties. Membrane binding is a crucial issue for these enzymes because of the high hydrophobicity of their retinoid substrates.
authors.affiliation: a CUO-Recherche, Centre de recherche du CHU de Québec, Hôpital du Saint Sacrement, Département d'ophtalmologie, Faculté de médicine, Université Laval, Québec, QC G1S 4L8, Canada.
authors.forename: Mustapha
authors.initials: M
authors.lastname: Lhor
authors.forename: Christian
authors.initials: C
authors.lastname: Salesse
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D055213:Retinal Pigment Epithelium / Q000201:enzymology*; D012243:Rhodopsin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D012243:Rhodopsin; D000429:Alcohol Oxidoreductases; C022520:retinol dehydrogenase
keywords: RDH; cycle visuel; membrane; oxidoreduction; oxydoréduction; photoreceptor; photorécepteur; retinal pigment epithelium; visual cycle; épithélium pigmentaire rétinien