Anaerobic oxidation of p-cresol mediated by a partially purified methylhydroxylase from a denitrifying bacterium

J Bacteriol. 1989 Jun;171(6):2956-62. doi: 10.1128/jb.171.6.2956-2962.1989.


Anoxic cell extracts of a denitrifying bacterial isolate (PC-07) were shown to oxidize p-cresol to p-hydroxybenzoate. Oxidation of the substrate was independent of molecular oxygen and required nitrate as the natural terminal electron acceptor. Two enzyme activities were implicated in the pathway utilized by PC-07. A p-cresol methylhydroxylase mediated the oxidation of p-cresol to p-hydroxybenzaldehyde, which was further oxidized to p-hydroxybenzoate by an NAD+-dependent dehydrogenase. The PC-07 methylhydroxylase was partially purified by anion-exchange chromatography. The protein appeared to be a multifunctional flavocytochrome, which first oxidized p-cresol to p-hydroxybenzyl alcohol, which was then oxidized to p-hydroxybenzaldehyde. The identity of the aldehyde was confirmed by mass spectroscopy. The PC-07 methylhydroxylase had a limited substrate range and required an alkyl-substituted phenolic ring with a hydroxyl group in the para position. From the available evidence, p-cresol, a naturally occurring phenol, exhibited the greatest affinity to the enzyme and therefore may be its natural substrate.

Publication types

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

MeSH terms

  • Anaerobiosis
  • Bacteria / metabolism*
  • Cell-Free System
  • Cresols / metabolism*
  • Flavoproteins / metabolism
  • Mass Spectrometry
  • Mixed Function Oxygenases / isolation & purification
  • Mixed Function Oxygenases / metabolism*
  • Nitrates / physiology
  • Oxidation-Reduction
  • Substrate Specificity


  • Cresols
  • Flavoproteins
  • Nitrates
  • 4-cresol
  • Mixed Function Oxygenases
  • 4-cresol dehydrogenase (hydroxylating)