Chlumsky L J, Zhang L, Jorns M S
Department of Biological Chemistry, Hahnemann University School of Medicine, Philadelphia, Pennsylvania 19102, USA.
J Biol Chem. 1995 Aug 4;270(31):18252-9. doi: 10.1074/jbc.270.31.18252.
Corynebacterial sarcosine oxidase, a heterotetrameric (alpha beta gamma delta) enzyme containing covalent and noncovalent FAD, catalyzes the oxidative demethylation of sarcosine to yield glycine, H2O2, and 5,10-CH2-tetrahydrofolate (H4folate) in a reaction requiring H4folate and O2. The sarcosine oxidase operon contains at least five closely packed genes encoding sarcosine oxidase subunits and serine hydroxymethyltransferase (glyA), arranged in the order glyAsoxBDAG. The operon status of a putative purU gene, found 340 nucleotides downstream from soxG, is not known. No homology with other proteins is observed for the smallest sarcosine oxidase subunits gamma and delta. The beta subunit (405 residues) contains an ADP-binding motif near its NH2 terminus, the covalent FAD attachment site (H175), and exhibits homology with the NH2-terminal half of dimethylglycine dehydrogenase (857 residues) and monomeric, bacterial sarcosine oxidases (approximately 388 residues), enzymes that contain a single covalent FAD. The alpha subunit (967 residues) contains a second ADP-binding motif within an approximately 280 residue region near the NH2 terminus that exhibits homology with subunit A from octopine and nopaline oxidases, heterodimeric enzymes that catalyze analogous oxidative cleavage reactions with N-substituted arginine derivatives. An approximately 380 residue region near the COOH terminus of alpha exhibits homology with T-protein and the COOH-terminal half of dimethylglycine dehydrogenase. These enzymes catalyze the formation of 5,10-CH2-H4folate, using different one-carbon donors. The results suggest that the alpha subunit and dimethylglycine dehydrogenase contain an NH2-terminal domain that binds noncovalent or covalent FAD, respectively, and a carboxyl-terminal H4folate-binding domain.
棒状杆菌肌氨酸氧化酶是一种异源四聚体（αβγδ）酶，含有共价和非共价结合的黄素腺嘌呤二核苷酸（FAD），在需要四氢叶酸（H4folate）和氧气的反应中，催化肌氨酸的氧化脱甲基反应，生成甘氨酸、过氧化氢和5,10-亚甲基四氢叶酸（H4folate）。肌氨酸氧化酶操纵子至少包含五个紧密排列的基因，编码肌氨酸氧化酶亚基和丝氨酸羟甲基转移酶（glyA），其排列顺序为glyAsoxBDAG。在soxG下游340个核苷酸处发现的一个假定的purU基因的操纵子状态尚不清楚。最小的肌氨酸氧化酶亚基γ和δ与其他蛋白质没有同源性。β亚基（405个残基）在其氨基末端附近含有一个ADP结合基序、共价FAD附着位点（H175），并且与二甲基甘氨酸脱氢酶（857个残基）的氨基末端一半以及单体细菌肌氨酸氧化酶（约388个残基）具有同源性，这些酶都含有单个共价FAD。α亚基（967个残基）在氨基末端附近约280个残基区域内含有第二个ADP结合基序，该区域与章鱼碱和胭脂碱氧化酶的A亚基具有同源性，章鱼碱和胭脂碱氧化酶是催化与N-取代精氨酸衍生物类似的氧化裂解反应的异源二聚体酶。α亚基羧基末端附近约380个残基区域与T蛋白以及二甲基甘氨酸脱氢酶的羧基末端一半具有同源性。这些酶使用不同的一碳供体催化5,10-亚甲基-H4folate的形成。结果表明，α亚基和二甲基甘氨酸脱氢酶分别含有一个结合非共价或共价FAD的氨基末端结构域和一个羧基末端H4folate结合结构域。
