Oxidation of p-cresol and related compounds by a Pseudomonas

Publisher Website
Google Scholar
Abstract
Cell-free extracts obtained from a Pseudomonas sp. catalyzed the oxidation of p-cresol, p-hydroxybenzaldehyde, p-hydraxybenzoic acid and protocatechuic acid. The amounts of O2 utilized support evidence from experiments with whole cells that the compounds participate in a reaction sequence in that order. p-Hydroxybenzaldehyde was isolated as its 2:4-dinitrophenylhydrazone after freeze-dried cells had oxidized p-cresol. A pink insoluble fraction from centrifuging of disintegrated cells carried a cytochrome system and increased the rate of oxidation of p-cresol by cell-free extracts. Extracts that catalyzed the conversion of p-hydroxybenzaldehyde into p-hydroxybenzoic acid required DPN as cofactor. Other aromatic aldehydes with a hydroxyl group in position 4 also required DPN for conversion into the corresponding acids. The enzyme catalyzing hydroxylation of p-hydroxybenzoic acid was relatively labile, and, after treatment of extract with ammonium sulfate, p-hydroxybenzoic acid accummulated when p-cresol and p-hydroxybenzoldehyde were oxidized. Specificity requirements of this enzyme were also apparently more stringent, since 2:4-xylenol, 3:4-xylenol and 4-methylresorcinol were oxidized to derivatives of p-hydroxybenzoic acid, but no further. Ferrous ions were required for the oxidations of protocatechuic acid by extracts with an uptake of 1 mole of oxygen/mole of substrate. The end product of the reaction was isolated, but does not appear to be identical with any compound hitherto implicated in the biological fission of aromatic compounds.