Enright Jennifer M, Toomey Matthew B, Sato Shin-ya, Temple Shelby E, Allen James R, Fujiwara Rina, Kramlinger Valerie M, Nagy Leslie D, Johnson Kevin M, Xiao Yi, How Martin J, Johnson Stephen L, Roberts Nicholas W, Kefalov Vladimir J, Guengerich F Peter, Corbo Joseph C
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.
Curr Biol. 2015 Dec 7;25(23):3048-57. doi: 10.1016/j.cub.2015.10.018. Epub 2015 Nov 5.
Some vertebrate species have evolved means of extending their visual sensitivity beyond the range of human vision. One mechanism of enhancing sensitivity to long-wavelength light is to replace the 11-cis retinal chromophore in photopigments with 11-cis 3,4-didehydroretinal. Despite over a century of research on this topic, the enzymatic basis of this perceptual switch remains unknown. Here, we show that a cytochrome P450 family member, Cyp27c1, mediates this switch by converting vitamin A1 (the precursor of 11-cis retinal) into vitamin A2 (the precursor of 11-cis 3,4-didehydroretinal). Knockout of cyp27c1 in zebrafish abrogates production of vitamin A2, eliminating the animal's ability to red-shift its photoreceptor spectral sensitivity and reducing its ability to see and respond to near-infrared light. Thus, the expression of a single enzyme mediates dynamic spectral tuning of the entire visual system by controlling the balance of vitamin A1 and A2 in the eye.
一些脊椎动物物种已经进化出了将视觉敏感度扩展到人类视觉范围之外的方法。增强对长波长光敏感度的一种机制是用11-顺式3,4-二脱氢视黄醛取代光色素中的11-顺式视黄醛发色团。尽管对这个主题进行了一个多世纪的研究，但这种感知转换的酶学基础仍然未知。在这里，我们表明细胞色素P450家族成员Cyp27c1通过将维生素A1（11-顺式视黄醛的前体）转化为维生素A2（11-顺式3,4-二脱氢视黄醛的前体）来介导这种转换。斑马鱼中cyp27c1的敲除消除了维生素A2的产生，消除了动物将其光感受器光谱敏感度红移的能力，并降低了其对近红外光的视觉和反应能力。因此，单一酶的表达通过控制眼睛中维生素A1和A2的平衡来介导整个视觉系统的动态光谱调谐。
