Identification of catalytically important residues of the carotenoid 1,2-hydratases from Rubrivivax gelatinosus and Thiocapsa roseopersicina.
Identification of catalytically important residues of the carotenoid 1,2-hydratases from Rubrivivax gelatinosus and Thiocapsa roseopersicina.
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从rubrivivax明胶和硫代帕帕西氏菌中的类胡萝卜素1,2-氢蛋白酶的催化重要残基鉴定。
DOI：
10.1007/s00253-015-6998-y
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发表时间：
2016-02
影响因子：
5
通讯作者：
Arends IWCE
中科院分区：
文献类型：
--
作者：
Hiseni A;Otten LG;Arends IWCE
类胡萝卜素1,2-水合酶（CrtC）催化分离的碳-碳双键选择性加成水。虽然它们参与类胡萝卜素的生物合成途径已经被很好地理解，但这些水合酶将类胡萝卜素（如番茄红素）转化为相应的羟基化合物的机制却知之甚少。在胶冻红螨CrtC的His239、Trp241、Tyr266和Asp268位点鉴定出了关键残基（在roseopersicina中也鉴定出了相应的位置）。在这些位置的丙氨酸突变体被发现是完全不活跃的，这表明它们直接参与催化反应。我们得出的机制假设与最近研究的一类萜类环化酶类似，这些酶的活性位点含有高度酸性的天冬氨酸残基。我们提出一个类似的天冬氨酸残基，在所有假定的crtc中都是保守的，参与了番茄红素双键的初始质子化。本文的在线版本（doi:10.1007/s00253-015-6998-y）包含补充材料，仅供授权用户使用。
Carotenoid 1,2-hydratases (CrtC) catalyze the selective addition of water to an isolated carbon–carbon double bond. Although their involvement in the carotenoid biosynthetic pathway is well understood, little is known about the mechanism by which these hydratases transform carotenoids such as lycopene into the corresponding hydroxyl compounds. Key residues were identified at positions His239, Trp241, Tyr266, and Asp268 in CrtC from Rubrivivax gelatinosus (and corresponding positions in Thiocapsa roseopersicina). Alanine mutants at these positions were found to be completely inactive, suggesting their direct involvement in the catalytic reaction. Our resulting mechanistic hypothesis is in analogy with the recently studied class of terpenoid cyclase enzymes containing a highly acidic aspartic residue in their active site. We propose that a similar aspartic acid residue, which is conserved through all putative CrtCs, is involved in initial protonation of the double bond in lycopene. The online version of this article (doi:10.1007/s00253-015-6998-y) contains supplementary material, which is available to authorized users.