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Nikkomycin biosynthesis: formation of a 4-electron oxidation product during turnover of NikD with its physiological substrate
Journal article   Peer reviewed

Nikkomycin biosynthesis: formation of a 4-electron oxidation product during turnover of NikD with its physiological substrate

Robert C Bruckner, Guohua Zhao, David Venci and Marilyn Schuman Jorns
Biochemistry (Easton), v 43(28), pp 9160-9167
20 Jul 2004
PMID: 15248773

Abstract

Aminoglycosides - isolation & purification Chromatography, High Pressure Liquid - methods Oxidation-Reduction Oxygen - chemistry Aminoglycosides - biosynthesis Aminoglycosides - chemistry Ligands Antifungal Agents - chemistry Flavin-Adenine Dinucleotide - analysis Electrons
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.

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Biochemistry & Molecular Biology
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