Late stages of visual pigment photolysis in situ: Cones vs. rods
Late stages of visual pigment photolysis in situ: Cones vs. rods
复制标题
DOI：
10.1016/j.visres.2005.12.017
复制
发表时间：
2006-07-01
期刊：
影响因子：
1.8
通讯作者：
Govardovskii, V. I.
中科院分区：
文献类型：
--
作者：
Golobokova, E. Yu.;Govardovskii, V. I.
缓慢的光解反应和暗色素的再生构成了暗适应的机制，光感受器细胞在强光照射后恢复其敏感性。我们提供了金鱼视网膜中完整的视杆细胞和对红色和绿色敏感的视锥细胞中视觉色素光解后期的动力学数据。用快速扫描二向色性显微分光光度计对单个感光体进行了测量。我们发现，在视锥细胞中，视蛋白-全反式-3-脱氢-视网膜连接的水解在20℃时的半衰期约为5 S，几乎比视杆细胞快两个数量级。在两栖类视紫红质视紫红质棒中，视锥细胞中的3-脱氢视黄醇的产生速度大约是视黄醇的3倍；反应速度受到视黄醇脱氢酶催化的视网膜还原速度的限制。视锥细胞的3-脱氢视黄醇/视黄醇Schiff碱的快速水解性和相应的暗视色素再生底物(游离视黄素和3-脱氢视黄醇)的快速出现，为视锥细胞(白天)比视杆细胞(夜间)更快的暗适应提供了必要条件。(C)2006爱思唯尔有限公司。保留所有权利。
Slow photolysis reactions and the regeneration of the dark pigment constitute the mechanisms of dark adaptation whereby photoreceptor cells restore their sensitivity after bright illumination. We present data on the kinetics of the late stages of the photolysis of the visual pigment in intact rods and red- and green-sensitive cones of the goldfish retina. Measurements were made on single photoreceptors by means of a fast-scanning dichroic microspectrophotometer. We show that in cones the hydrolysis of the opsin-all-trans 3-dehydro-retinal linkage proceeds with a half-time of approximate to 5 s at 20 degrees C that is almost two orders of magnitude faster than in rods. 3-Dehydroretinol in cones is produced approximate to 3-fold faster than retinol in amphibian rhodopsin rods; the rate of the reaction is limited by the speed of retinal reduction catalyzed by retinoldehydrogenase. The fast hydrolysis of the 3-dehydroretinal/opsin Schiff base and the correspondingly fast appearance of the substrates for dark visual pigment regeneration (free opsin and 3-dehydroretinol) provide essential conditions for faster dark adaptation of cone (diurnal) as compared to rod (nocturnal) vision. (c) 2006 Elsevier Ltd. All rights reserved.