Bacterial metabolism of 5-aminosalicylic acid: enzymic conversion to L-malate, pyruvate and ammonia.

5-Aminosalicylate (5AS) was converted to L-malate, pyruvate and ammonia by cell-free extracts from Pseudomonas sp. BN9 in the presence of glutathione. In the absence of glutathione, 5AS was oxidized to the ring-fission product cis-4-amino-6-carboxy-2-oxo-hexa-3,5-dienoate (cis-ACOHDA). Glutathione catalysed the spontaneous isomerization of cis-ACOHDA to its trans-isomer. The same reaction was catalysed by light and by acidic conditions. trans-ACOHDA was enzymically deaminated to fumarylpyruvate (trans-2,4-dioxo-5-hexenoate). The trans-ACOHDA hydrolase was induced after growth of Pseudomonas sp. BN9 with 5AS, but not after growth with acetate or nutrient broth. At the fumarylpyruvate stage, the metabolism of 5AS converged with a pathway described for the degradation of gentisate. Fumarylpyruvate was cleaved by Pseudomonas sp. BN9 to fumarate and pyruvate.