Department of Ophthalmology and Biochemistry, University of Washington, Seattle, WA 91895, USA.
Annu Rev Nutr. 2012 Aug 21;32:125-45. doi: 10.1146/annurev-nutr-071811-150748.
The chromophore of all known visual pigments consists of 11-cis-retinal (derived from either vitamin A1 or A2) or a hydroxylated derivative, bound to a protein (opsin) via a Schiff base. Absorption of a photon results in photoisomerization of the chromophore to all-trans-retinal and conversion of the visual pigment to the signaling form. Regeneration of the 11-cis-retinal occurs in an adjacent tissue and involves several enzymes, several water-soluble retinoid-binding proteins, and intra- and intercellular diffusional processes. Rod photoreceptor cells depend completely on the output of 11-cis-retinal from adjacent retinal pigment epithelial (RPE) cells. Cone photoreceptors cells can use 11-cis-retinal from the RPE and from a second more poorly characterized cycle, which appears to involve adjacent Müller (glial) cells. Recent progress in the characterization of rod and cone visual cycle components and reactions will result in the development of approaches to the amelioration of blinding eye diseases associated with visual cycle defects.
所有已知视觉色素的生色团都由 11-顺式视黄醛（来自维生素 A1 或 A2）或羟基化衍生物通过席夫碱与蛋白质（视蛋白）结合而成。光子的吸收导致生色团光异构化为全反式视黄醛，并将视觉色素转化为信号形式。11-顺式视黄醛的再生发生在相邻组织中，涉及几种酶、几种水溶性视黄醇结合蛋白以及细胞内和细胞间的扩散过程。视杆细胞完全依赖于相邻视网膜色素上皮 (RPE) 细胞输出的 11-顺式视黄醛。视锥细胞可以使用来自 RPE 的 11-顺式视黄醛和第二个特征较差的循环，后者似乎涉及相邻的 Müller（胶质）细胞。在描述视杆和视锥视觉循环成分和反应方面的最新进展将导致开发改善与视觉循环缺陷相关的致盲眼病的方法。
