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

Biochemistry. 2004 Jul 20;43(28):9160-7. doi: 10.1021/bi0493618.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

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

Substances

  • Aminoglycosides
  • Antifungal Agents
  • Ligands
  • Flavin-Adenine Dinucleotide
  • nikkomycin
  • Oxygen