Revealing the moonlighting role of NADP in the structure of a flavin-containing monooxygenase
Revealing the moonlighting role of NADP in the structure of a flavin-containing monooxygenase
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DOI：
10.1073/pnas.0800859105
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发表时间：
2008-05-06
影响因子：
11.1
通讯作者：
Mattevi, Andrea
中科院分区：
文献类型：
--
作者：
Alfieri, Andrea;Malito, Enrico;Mattevi, Andrea
含黄素单加氧酶（FMOs）是继细胞色素P450之后人类最重要的单加氧酶系统，参与外源性物质的代谢和药物反应的变化。来自嗜甲基菌属菌株SK 1的可溶性原核FMO的X射线结构已经在2.6埃分辨率下解析，并且现在是已知结构的蛋白质，其与人FMO具有最高的序列相似性。该结构具有双域结构，FAD和NIADP（+）都很好地定义了电子密度图。生物化学分析表明，原核酶与哺乳动物FMO具有许多功能特性，包括底物特异性和稳定氢过氧黄素中间体的能力，这在底物氧化中至关重要。根据它们在结构中的位置，NIADP（+）的烟酰胺环和相邻的核糖原来是催化位点的组成部分，积极参与氧化中间体的稳定。这一特征表明NADP（H）具有兼职作用，因为它采用两种结合模式，使其分别在黄素还原和氧反应性调节中发挥作用。我们假设，需要一个相对的域旋转，使NADP（H）的这些不同的位置内的活性位点。在人类FMO 3中已知引起三甲基氨基尿症（鱼腥味综合征）的突变在阐明的FMO结构中的定位为其生物学效应提供了结构解释。
Flavin-containing monooxygenases (FMOs) are, after cytochromes P450, the most important monooxygenase system in humans and are involved in xenobiotics metabolism and variability in drug response. The x-ray structure of a soluble prokaryotic FMO from Methylophaga sp. strain SK1 has been solved at 2.6-angstrom resolution and is now the protein of known structure with the highest sequence similarity to human FMOs. The structure possesses a two-domain architecture, with both FAD and NIADP(+) well defined by the electron density maps. Biochemical analysis shows that the prokaryotic enzyme shares many functional properties with mammalian FMOs, including substrate specificity and the ability to stabilize the hydroperoxyflavin intermediate that is crucial in substrate oxygenation. On the basis of their location in the structure, the nicotinamide ring and the adjacent ribose of NIADP(+) turn out to be an integral part of the catalytic site being actively engaged in the stabilization of the oxygenating intermediate. This feature suggests that NADP(H) has a moonlighting role, in that it adopts two binding modes that allow it to function in both flavin reduction and oxygen reactivity modulation, respectively. We hypothesize that a relative domain rotation is needed to bring NADP(H) to these distinct positions inside the active site. Localization of mutations in human FMO3 that are known to cause trimethylaminuria (fish-odor syndrome) in the elucidated FMO structure provides a structural explanation for their biological effects.