A novel pathway of aerobic benzoate catabolism in the bacteria Azoarcus evansii and Bacillus stearothermophilus

The aerobic catabolism of benzoate was studied in the Gram-negative proteob acterium Azoarcus evansii and in the Gram-positive bacterium Bacillus stear othermophilus, In contrast to earlier proposals, benzoate was not converted into hydroxybenzoate or gentisate, Rather, benzoyl-CoA was a product of be nzoate catabolism in both microbial species under aerobic conditions in viv o. Benzoyl-CoA was converted into various CoA thioesters by cell extracts o f both species in oxygen- and NADPH-dependent reactions. Using [ring-C-13(6 )]benzoyl-CoA as substrate, cis-3,4-[2,3,4,5,6-C-13(5)]dehydroadipyl-CoA, t rans-2,3-[2,3,4,5,6-C-13(5)]dehydroadipyl-CoA, the 3,6-lactone of 3-[2,3,4, 5,6-C-13(5)]hydroxyadipyl-CoA, and 3-[2,3, 4,5,6-C-13(5)]hydroxyadipyl-CoA were identified as products by MMR spectroscopy. A protein mixture of A. ev ansii transformed [ring-C-13(6)]benzoyl-CoA in an NADPH- and oxygen-depende nt reaction into 6-[2,3,4,5,6-C-13(5)]hydroxy-3-hexenoyl-CoA. The data sugg est a novel aerobic pathway of benzoate catabolism via CoA intermediates le ading to beta -ketoadipyl-CoA, an intermediate of the known beta -ketoadipa te pathway.