Nikkomycin biosynthesis: Formation of a 4-electron oxidation product during turnover of NikD with its physiological substrate
Nikkomycin biosynthesis: Formation of a 4-electron oxidation product during turnover of NikD with its physiological substrate
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DOI：
10.1021/bi0493618
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发表时间：
2004-07-20
期刊：
影响因子：
2.9
通讯作者：
Jorns, MS
中科院分区：
文献类型：
--
作者：
Bruckner, RC;Zhao, GH;Jorns, MS
尼可霉素是肽基核苷抗生素，在人类中用作治疗性抗真菌剂，在农业中用作易于降解的杀虫剂。尼可霉素肽基部分含有衍生自 L-赖氨酸的吡啶基残基。肽基生物合成的第一步是转氨酶催化的反应，将 L-赖氨酸转化为 Delta(1)-或 Delta(2)-哌啶-2-羧酸酯 (P2C)。光谱、色谱和动力学分析表明，nikD 与 P2C 的有氧反应导致化学计量形成吡啶甲酸酯，同时将 2 mol 氧气还原为过氧化氢。开发了一种能够分离吡啶甲酸、烟酸和异烟酸的高分辨率HPLC方法并用于产品鉴定。 NikD 含有 1 mol 共价结合的 FAD，并以单体形式存在于溶液中。分别用连二亚硫酸盐和铁氰化钾进行还原滴定和氧化滴定表明FAD是nikD中唯一的氧化还原活性基团。 nikD 与 1 mol P2C 发生厌氧反应，导致酶结合的 FAD 立即减少。由于 nikD 是专性 2 电子受体，因此推测观察到的 P2C 4 电子氧化为吡啶甲酸是通过涉及两个连续 nikD 催化 2 电子氧化步骤的机制发生的。除了尼可霉素之外，类似 nikD 的反应也参与了链阳菌素 B 组抗生素中发现的 L-赖氨酸衍生吡啶基部分的生物合成，链阳菌素 B 类抗生素被用作治疗革兰氏阳性菌严重感染的最后手段的一部分。
Nikkomycins are peptidyl nucleoside antibiotics that act as therapeutic antifungal agents in humans and easily degraded insecticides in agriculture. The nikkomycin peptidyl moiety contains a pyridyl residue derived from L-lysine. The first step in peptidyl biosynthesis is an aminotransferase-catalyzed reaction that converts L-lysine to Delta(1)- or Delta(2)-piperideine-2-carboxylate (P2C). Spectral, chromatographic, and kinetic analyses show that the aerobic reaction of nikD with P2C results in the stoichiometric formation of picolinate, accompanied by the reduction of 2 mol of oxygen to hydrogen peroxide. A high resolution HPLC method, capable of separating picolinate, nicotinate and isonicotinate, was developed and used in product identification. NikD contains 1 mol of covalently bound FAD and exists as a monomer in solution. Reductive and oxidative titrations with dithionite and potassium ferricyanide, respectively, show that FAD is the only redox-active group in nikD. Anaerobic reaction of nikD with 1 mol of P2C results in immediate reduction of enzyme-bound FAD. Because nikD is an obligate 2-electron acceptor, it is proposed that the observed 4-electron oxidation of P2C to picolinate occurs via a mechanism involving two successive nikD-catalyzed 2-electron oxidation steps. In addition to nikkomycins, a nikD-like reaction is implicated in the biosynthesis of an L-lysine-derived pyridyl moiety found in streptogramin group B antibiotics that are used as part of a last resort treatment for severe infections due to gram positive bacteria.