A novel type of P450c17 lacking the lyase activity is responsible for C21-steroid biosynthesis in the fish ovary and head kidney.
A novel type of P450c17 lacking the lyase activity is responsible for C21-steroid biosynthesis in the fish ovary and head kidney.
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DOI：
10.1210/en.2007-0487
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发表时间：
2007-09
期刊：
影响因子：
4.8
通讯作者：
Lin-Yan Zhou;De-shou Wang;Tohru Kobayashi;A. Yano;B. Paul-Prasanth;A. Suzuki;F. Sakai;Y. Nagahama-Y.-N
中科院分区：
文献类型：
--
作者：
Lin-Yan Zhou;De-shou Wang;Tohru Kobayashi;A. Yano;B. Paul-Prasanth;A. Suzuki;F. Sakai;Y. Nagahama-Y.-N
细胞色素P450 c17是在性腺和肾上腺中类固醇激素生物合成期间介导17 α-羟化酶和17，20裂解酶活性的单一酶。然而，其双重作用的机制仍然是鱼类类固醇合成领域的争议。为了解决这个问题，我们通过计算机分析从六种鱼类的基因组中鉴定出一种新的P450 c17（P450 c17-II）。我们从罗非鱼和青鳉鱼中克隆了P450 c17-II，并与传统的P450 c17-I进行了比较，发现它们在基因结构和酶活性方面存在差异。通过薄层层析进行的酶测定显示，P450 c17-II仅具有17 α-羟化酶活性而不具有任何17，20裂解酶活性，而P450 c17-I具有这两种活性。P450 c17-I和-II在睾丸间质细胞均有表达。显着的差异，原位杂交显示，在卵巢和头肾的罗非鱼在不同的发展阶段的P450 c17-I和-II的表达模式强烈表明，P450 c17-I是负责在卵巢中的雌二醇-17 β的合成，而P450 c17-II是必要的生产C21类固醇，如皮质醇在头肾。更有趣的是，在鱼卵巢中从雌二醇-17 β到C21类固醇，17 α，20 β-二羟基-4-异戊烯-3-酮（鱼类卵母细胞的成熟诱导激素）的类固醇生成转变期间，在这两个基因的表达中观察到时间控制的切换，揭示了P450 c17-II在诱导鱼类卵母细胞成熟的激素产生中的作用。
Cytochrome P450c17 is the single enzyme that mediates the 17 alpha-hydroxylase and 17, 20 lyase activities during the biosynthesis of steroid hormones in the gonads and adrenal gland. However, the mechanism underlying its dual action continues to be a controversy in the field of steroidogenesis in fish. In an attempt to resolve this issue, we identified a novel type of P450c17 (P450c17-II) by an in silico analysis from the genomes of six fish species. We cloned P450c17-II from tilapia and medaka, and comparison with the conventional P450c17-I revealed that they differ in gene structure and enzymatic activity. Enzymatic assays by thin-layer chromatography revealed that P450c17-II possesses only the 17 alpha-hydroxylase activity without any 17, 20 lyase activity, unlike P450c17-I, which has both these activities. In testis, both P450c17-I and -II express in the interstitial cells. Remarkable differences, revealed by in situ hybridization, in the expression patterns of the P450c17-I and -II in the ovary and head kidney of tilapia during various stages of development strongly suggest that P450c17-I is responsible for the synthesis of estradiol-17beta in the ovary, whereas P450c17-II is required for the production of C21 steroids such as cortisol in the head kidney. More interestingly, a temporally controlled switching is observable in the expression of these two genes during the steroidogenic shift from estradiol-17beta to the C21 steroid, 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (maturation-inducing hormone of fish oocytes) in the fish ovary, revealing a role for P450c17-II in the production of hormones that induce oocyte maturation in fish.