Biochemical properties of purified human retinol dehydrogenase 12 (RDH12):: Catalytic efficiency toward Retinoids and C9 aldehydes and effects of cellular retinol-binding protein type I (CRBPI) and cellular retinaldehyde-binding protein (CRALBP) on the oxidation and reduction of retinoids
Biochemical properties of purified human retinol dehydrogenase 12 (RDH12):: Catalytic efficiency toward Retinoids and C9 aldehydes and effects of cellular retinol-binding protein type I (CRBPI) and cellular retinaldehyde-binding protein (CRALBP) on the oxidation and reduction of retinoids
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DOI：
10.1021/bi050226k
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发表时间：
2005-05-10
期刊：
影响因子：
2.9
通讯作者：
Kedishvili, NY
中科院分区：
文献类型：
--
作者：
Belyaeva, OV;Korkina, OV;Kedishvili, NY
视黄醇脱氢酶12 （RDH12）是短链脱氢酶/还原酶超家族蛋白的新成员，最近与Leber's先天性黑朦3 （LCA）有关。我们报道了纯化的人RDH12的第一个生化特性和分析其在人体组织中的表达。RDH12对NADP+和NADPH的Km值比对NAD（+）和NADH的Km值低2000倍，并能识别类维生素a和脂质过氧化产物（C-9醛）作为底物。视黄醛和C-9醛的RDH12的k（cat）值相似，但类视黄醛的k -m值一般较低。该酶对全反式视网膜的催化效率最高(k(cat)/ k -m，接近900 min(-1) μ M-1)，其次是11-顺式视网膜(450 min（-1) mM(-1)）和9-顺式视网膜(100 min（-1) mM(-1)）。分析RDH12在细胞视黄醇结合蛋白（CRBP） I型或细胞视黄醛结合蛋白（CRALBP）存在下对类维甲酸的活性表明，RDH12利用了全反式和11顺式非结合形式的类维甲酸。因此，广泛表达的CRBPI与全反式视黄醇结合的亲和力远高于全反式视黄醛，它限制了RDH12对全反式视黄醇的氧化，但对全反式视黄醇的还原作用几乎没有影响，CRALBP对11-顺式视黄醇的还原作用强于对11-顺式视黄醇的氧化作用，这与CRALBP对11-顺式视黄醇的高亲和力相一致。总之，RDH12的组织分布及其催化性能表明，在大多数组织中，RDH12主要参与全反式视黄醛的还原；然而，在经受氧化应激的细胞（例如光感受器）中过氧化醛的饱和浓度下，RDH12也可能在脂质过氧化产物的解毒中发挥作用。
Retinol dehydrogenase 12 (RDH12) is a novel member of the short-chain dehydrogenase/ reductase superfamily of proteins that was recently linked to Leber's congenital amaurosis 3 (LCA). We report the first biochemical characterization of purified human RDH12 and analysis of its expression in human tissues. RDH12 exhibits similar to 2000-fold lower Km values for NADP+ and NADPH than for NAD(+) and NADH and recognizes both retinoids and lipid peroxidation products (C-9 aldehydes) as substrates. The k(cat) values of RDH12 for retinaldehydes and C-9 aldehydes are similar, but the K-m values are, in general, lower for retinoids. The enzyme exhibits the highest catalytic efficiency for all-trans-retinal (k(cat)/ K-m similar to 900 min(-1) mu M-1), followed by 11-cis-retinal (450 min(-1) mM(-1)) and 9-cis-retinal (100 min(-1) mM(-1)). Analysis of RDH12 activity toward retinoids in the presence of cellular retinol-binding protein (CRBP) type I or cellular retinaldehyde-binding protein (CRALBP) suggests that RDH12 utilizes the unbound forms of all-trans- and 11-cis-retinoids. As a result, the widely expressed CRBPI, which binds all-transretinol with much higher affinity than all-trans-retinaldehyde, restricts the oxidation of all-trans-retinol by RDH12, but has little effect on the reduction of all-trans-retinaldehyde, and CRALBP inhibits the reduction of 11-cis-retinal stronger than the oxidation of 11-cis-retinol, in accord with its higher affinity for 11-cis-retinal. Together, the tissue distribution of RDH12 and its catalytic properties suggest that, in most tissues, RDH12 primarily contributes to the reduction of all-trans-retinaldehyde; however, at saturating concentrations of peroxidic aldehydes in the cells undergoing oxidative stress, for example, photoreceptors, RDH12 might also play a role in detoxification of lipid peroxidation products.