Products of enzymatic reduction of benzoyl‐CoA, a key reaction in anaerobic aromatic metabolism

• DOI: 10.1111/j.1432-1033.1993.tb17593.x
• Publication Date: 2005-03-04T08:26:52Z
• Authors: Jürgen KOCH; Wolfgang EISENREICH; Adelbert BACHER; Georg FUCHS
• Keywords: Birch reduction; Metabolic intermediate; Coenzyme A; Pseudomonas putida

Benzoyl‐coenzyme A is the most common central intermediate of anaerobic aromatic metabolism. Studies with whole cells different bacteria and in vitro had shown that benzoyl‐CoA reduced to alicyclic compounds, possibly via cyclohexadiene intermediates. This reaction considered a ‘biological Birch reduction’. We have elucidated by NMR techniques structures six products [ ring ‐ 13 C 6 ]benzoate reduction. The catalyzed extracts from denitrifying Pseudomonas strain K172 anaerobically grown benzoate nitrate as sole carbon energy sources. assay mixture contained [ring‐ plus traces [U‐ 14 C]benzoate, Mg 2+ , ATP, coenzyme (CoA), Ti(III) reductant. use multiply C‐labelled precursor increases sensitivity detection allows analysis crude product mixtures two‐dimensional coherence transfer procedures such total correlation C‐NMR spectroscopy C‐filtered 1 H‐NMR spectroscopy. time course formation consistent following order events. Benzoyl‐CoA formed benzoate‐CoA ligase. first reduction observed cyclohex‐1,5‐diene‐1‐carboxyl‐CoA. next 6‐hydroxycyclohex‐1‐ene‐1‐carboxyl‐CoA which derived diene addition water. Part seems be cyclohex‐1‐ene‐1‐carboxyl‐CoA becomes hydrated trans ‐2‐hydroxycyclohexane‐1‐carboxyl‐CoA; these two intermediates may side vitro. non‐cyclic β‐oxidation 3‐hydroxypimelyl‐CoA. aliphatic 7 dicarboxylic acid proposed oxidized glutaryl‐CoA crotonyl‐CoA three molecules acetyl‐CoA one molecule CO 2 . similar pattern was benzoate‐degrading phototrophic bacterium Rhodopseudomonas palustris. indicates enzymatic mechanistically anaerobes.