New enzymes involved in aerobic benzoate metabolism in Azoarcus evansii

Mol Microbiol. 2004 Oct;54(1):223-38. doi: 10.1111/j.1365-2958.2004.04263.x.


A new principle of aerobic aromatic metabolism has been postulated, which is in contrast to the known pathways. In various bacteria the aromatic substrate benzoate is first converted to its coenzyme A (CoA) thioester, benzoyl-CoA, which is subsequently attacked by an oxygenase, followed by a non-oxygenolytic fission of the ring. We provide evidence for this hypothesis and show that benzoyl-CoA conversion in the bacterium Azoarcus evansii requires NADPH, O(2) and two protein components, BoxA and BoxB. BoxA is a homodimeric 46 kDa iron-sulphur-flavoprotein, which acts as reductase. In the absence of BoxB, BoxA catalyses the benzoyl-CoA stimulated artificial transfer of electrons from NADPH to O(2) via free FADH(2) to produce H(2)O(2). Physiologically, BoxA uses NADPH to reduce BoxB, a monomeric 55 kDa iron-protein that acts as benzoyl-CoA oxygenase. The product of benzoyl-CoA oxidation was identified by NMR spectroscopy as its dihydrodiol derivative, 2,3-dihydro-2,3-dihydroxybenzoyl-CoA. This suggests that BoxBA act as a benzoyl-CoA dioxygenase/reductase. Unexpectedly, benzoyl-CoA transformation by BoxBA was greatly stimulated when another enoyl-CoA hydratase/isomerase-like protein, BoxC, was added that catalysed the further transformation of the dihydrodiol product formed from benzoyl-CoA. The benzoyl-CoA oxygenase system has very low similarity to known (di)oxygenase systems and is the first member of a new enzyme family.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyl Coenzyme A / metabolism*
  • Aerobiosis
  • Amino Acid Sequence
  • Azoarcus / enzymology*
  • Azoarcus / genetics
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Benzoates / metabolism*
  • Chromatography, High Pressure Liquid
  • Coenzyme A Ligases / metabolism
  • Consensus Sequence
  • Magnetic Resonance Spectroscopy
  • Molecular Sequence Data
  • NADP / metabolism
  • Oxidation-Reduction
  • Oxygen / metabolism
  • Oxygenases* / chemistry
  • Oxygenases* / genetics
  • Oxygenases* / metabolism


  • Acyl Coenzyme A
  • Bacterial Proteins
  • Benzoates
  • NADP
  • benzoyl-coenzyme A
  • Oxygenases
  • Coenzyme A Ligases
  • Oxygen