Anaerobic oxidation of p-cresol mediated by a partially purified methylhydroxylase from a denitrifying bacterium.
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.
Bossert
I D
ID
Department of Microbiology, New York University Medical Center, New York 10016.
Whited
G
G
Gibson
D T
DT
Young
L Y
LY
D000693:Anaerobiosis; D001419:Bacteria / Q000378:metabolism*; D002474:Cell-Free System; D003408:Cresols / Q000378:metabolism*; D005420:Flavoproteins / Q000378:metabolism; D013058:Mass Spectrometry; D006899:Mixed Function Oxygenases / Q000302:isolation & purification / Q000378:metabolism*; D009566:Nitrates / Q000502:physiology; D010084:Oxidation-Reduction; D013379:Substrate Specificity
D003408:Cresols; D005420:Flavoproteins; D009566:Nitrates; C032538:4-cresol; D006899:Mixed Function Oxygenases; C049502:4-cresol dehydrogenase (hydroxylating)