Bacterial degradation of 3,4,5-trimethoxyphenylacetic and 3-ketoglutaric acids

When grown at the expense of 3,4,5-trimethoxyphenylacetic acid, a species of Arthrobacter readily oxidized 3,4-dihydroxy-5-methoxyphenylacetic acid, but other structurally related aromatic acids were oxidized only slowly. Cell extracts contained a dioxygenase for 3,4-dihydroxy-5-methoxyphenylacetate, and the corresponding trihydroxy acid, which was not attacked by the enzyme, inhibited oxidation of this ring-fission substrate. Cell suspensions did not release carbon dioxide from 3,4-[methoxyl-14C]dihydroxy-5-methoxyphenylacetate but accumulated 1 mol of methanol per mol of 3,4,5-trimethoxyphenylacetate oxidized. A cell extract converted the ring-fission substrate into stoichiometric amounts of pyruvate and acetoacetate, formed from 3-ketoglutarate by the action of an induced decarboxylase. 3-Ketoglutaric acid served as sole source of carbon for many soil isolates.