Mechanism of action of a flavin-containing monooxygenase
Mechanism of action of a flavin-containing monooxygenase
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DOI：
10.1073/pnas.0602398103
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发表时间：
2006-06-27
影响因子：
11.1
通讯作者：
Swaminathan, Subramanyam
中科院分区：
文献类型：
--
作者：
Eswaramoorthy, Subramaniam;Bonanno, Jeffrey B.;Swaminathan, Subramanyam
消除非营养性和不溶性化合物对任何生物来说都是一项重要的任务。含有黄素的单加氧酶(FMOS)将氧原子结合到不溶的亲核化合物上，以增加溶解度，从而增加排泄量。在这里，我们利用野生型、蛋白质辅因子和蛋白质底物复合体的晶体结构来分析裂殖酵母FMO的作用机制。野生型FMO的结构表明，修复基团FAD是蛋白质的组成部分。FMO的催化活性除了需要辅基外，还需要NADPH作为辅因子。蛋白质-辅因子和蛋白质-底物复合体的结构提供了对作用机制的见解。我们认为，FMOS作为一种复合体存在于细胞中，它具有还原形式的假体基团和NADPH辅因子，使它们能够作用于底物。修复基团的4α-氢过氧黄素形式代表单氧化过程的瞬时中间体。含氧和还原形式的修复基团有助于交替稳定与辅因子和底物的相互作用，以实现持续的酶周转。
Elimination of nonnutritional and insoluble compounds is a critical task for any living organism. Flavin-containing monooxygenases (FMOs) attach an oxygen atom to the insoluble nucleophilic compounds to increase solubility and thereby increase excretion. Here we analyze the functional mechanism of FMO from Schizosaccharomyces pombe using the crystal structures of the wild type and protein-cofactor and protein-substrate complexes. The structure of the wild-type FMO revealed that the prosthetic group FAD is an integral part of the protein. FMO needs NADPH as a cofactor in addition to the prosthetic group for its catalytic activity. Structures of the protein-cofactor and protein-substrate complexes provide insights into mechanism of action. We propose that FMOs exist in the cell as a complex with a reduced form of the prosthetic group and NADPH cofactor, readying them to act on substrates. The 4 alpha-hydroperoxyflavin form of the prosthetic group represents a transient intermediate of the monooxygenation process. The oxygenated and reduced forms of the prosthetic group help stabilize interactions with cofactor and substrate alternately to permit continuous enzyme turnover.