The utilization of some halogenated aromatic acids by Nocardia. Oxidation and metabolism

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Abstract
Halogen analogues of p-nitrobenzoate and benzoate were oxidized by washed cells of Nocardia erythropolis. The oxidation of 2-fluoro-4-nitro-benzoate ceased at the level of acetate, and fluoroacetate was found in the incubation medium and particularly in hot-ethanolic extracts of the cells. Several fluorine-containing intermediates were detected and 2-fluoroprotocatechuate was identified as 1 of them. The nitro group was also reduced by the organism, as evidenced by the formation of 4-amino-2-fluorobenzoate. Extracts of N. erythropolis activated fluoroacetate and condensed the resulting fluoroacetyl-CoA with oxalo-acetate to form fluorocitrate. This product was a very powerful inhibitor of citrate metabolism by guinea-pig kidney homogenates of the aconitase also present in the bacterial extracts. The inhibitions effected by synthetic fluorocitrate and the natural product were com -parable. 2-Fluoro-4-nitrobenzoate had negligible mammalian toxicity. The isolation of fluoroacetate as a product of 2-fluoro-4-nitrobenzoate oxidation implies that the aromatic ring in this bacterium must be degraded via a gamma-carboxymuconolactone; fluoroacetate cannot arise by metabolism through the isomeric [beta]-carboxymuconolactone.