Highly efficient retinal metabolism in cones
Highly efficient retinal metabolism in cones
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DOI：
10.1073/pnas.0806593105
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发表时间：
2008-10-14
影响因子：
11.1
通讯作者：
Kawamura, Satoru
中科院分区：
文献类型：
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作者：
Miyazono, Sadaharu;Shimauchi-Matsukawa, Yoshie;Kawamura, Satoru
脊椎动物光感受器中的视色素漂白后，全反式视网膜被视黄醇脱氢酶(RDHs)还原为全反式视黄醇。我们在纯化的鲤鱼视杆和视锥中研究了这一反应，我们发现视锥外节(OS)对全反式视网膜的还原活性是视锥的30倍。RDHs的高活性归因于球果中RDH8的高含量。在杆状和球果的内节(IS)中，RDH8L2和RDH13是RDH家族蛋白中的主要酶。我们进一步发现了一种先前未描述的有效途径来将11-顺式视黄醇转化为11-顺式视黄醇：这种氧化转化不需要NADP(+)，而是与全反式视黄醇的还原相结合。其活性是需要NADP(+)的RDHs氧化活性的50倍。RDH8去除全反式视网膜的这些高效反应以及通过偶联反应产生11顺式视网膜可能是确保视锥细胞在比视杆细胞更明亮的光线条件下有效再生视觉色素的潜在机制。
After bleaching of visual pigment in vertebrate photoreceptors, all-trans retinal is reduced to all-trans retinol by retinol dehydrogenases (RDHs). We investigated this reaction in purified carp rods and cones, and we found that the reducing activity toward all-trans retinal in the outer segment (OS) of cones is > 30 times higher than that of rods. The high activity of RDHs was attributed to high content of RDH8 in cones. In the inner segment (IS) in both rods and cones, RDH8L2 and RDH13 were found to be the major enzymes among RDH family proteins. We further found a previously undescribed and effective pathway to convert 11-cis retinol to 11-cis retinal in cones: this oxidative conversion did not require NADP(+) and instead was coupled with reduction of all-trans retinal to all-trans retinol. The activity was > 50 times effective than the oxidizing activity of RDHs that require NADP(+). These highly effective reactions of removal of all-trans retinal by RDH8 and production of 11-cis retinal by the coupling reaction are probably the underlying mechanisms that ensure effective visual pigment regeneration in cones that function under much brighter light conditions than rods.