Metabolism of p -Cresol by the Fungus Aspergillus fumigatus

Abstract

The fungus Aspergillus fumigatus ATCC 28282 was shown to grow on p -cresol as its sole source of carbon and energy. A pathway for metabolism of this compound was proposed. This has protocatechuate as the ring-fission substrate with cleavage and metabolism by an ortho -fission pathway. The protocatechuate was formed by two alternative routes, either by initial attack on the methyl group, which is oxidized to carboxyl, followed by ring-hydroxylation, or by ring-hydroxylation as the first step with subsequent oxidation of 4-methylcatechol to the acid. The pathway was elucidated from several pieces of evidence. A number of compounds, including 4-hydroxybenzyl alcohol, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, protocatechuic acid, protocatechualdehyde, and 4-methylcatechol, appeared transiently in the medium during growth on p -cresol. These compounds were oxidized without lag by p -cresol-grown cells but not by succinate-grown cells. Enzyme activities for most of the proposed steps were demonstrated in cell extracts after growth on p -cresol, and the products of these activities were identified. None of the activities were found in succinate-grown cells.