Genes coding for a new pathway of aerobic benzoate metabolism in Azoarcus evansii

J Bacteriol. 2002 Nov;184(22):6301-15. doi: 10.1128/jb.184.22.6301-6315.2002.

Abstract

A new pathway for aerobic benzoate oxidation has been postulated for Azoarcus evansii and for a Bacillus stearothermophilus-like strain. Benzoate is first transformed into benzoyl coenzyme A (benzoyl-CoA), which subsequently is oxidized to 3-hydroxyadipyl-CoA and then to 3-ketoadipyl-CoA; all intermediates are CoA thioesters. The genes coding for this benzoate-induced pathway were investigated in the beta-proteobacterium A. evansii. They were identified on the basis of N-terminal amino acid sequences of purified benzoate metabolic enzymes and of benzoate-induced proteins identified on two-dimensional gels. Fifteen genes probably coding for the benzoate pathway were found to be clustered on the chromosome. These genes code for the following functions: a putative ATP-dependent benzoate transport system, benzoate-CoA ligase, a putative benzoyl-CoA oxygenase, a putative isomerizing enzyme, a putative ring-opening enzyme, enzymes for beta-oxidation of CoA-activated intermediates, thioesterase, and lactone hydrolase, as well as completely unknown enzymes belonging to new protein families. An unusual putative regulator protein consists of a regulator protein and a shikimate kinase I-type domain. A deletion mutant with a deletion in one gene (boxA) was unable to grow with benzoate as the sole organic substrate, but it was able to grow with 3-hydroxybenzoate and adipate. The data support the proposed pathway, which postulates operation of a new type of ring-hydroxylating dioxygenase acting on benzoyl-CoA and nonoxygenolytic ring cleavage. A beta-oxidation-like metabolism of the ring cleavage product is thought to lead to 3-ketoadipyl-CoA, which finally is cleaved into succinyl-CoA and acetyl-CoA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aerobiosis
  • Amino Acid Sequence
  • Azoarcus / genetics
  • Azoarcus / growth & development
  • Azoarcus / metabolism*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Benzoates / metabolism*
  • Biodegradation, Environmental
  • Cloning, Molecular
  • Electrophoresis, Gel, Two-Dimensional
  • Gene Expression Regulation, Bacterial
  • Molecular Sequence Data
  • Multigene Family*
  • Open Reading Frames / genetics
  • Sequence Analysis, DNA

Substances

  • Bacterial Proteins
  • Benzoates

Associated data

  • GENBANK/AF548005