Enzymes of the beta-ketoadipate pathway are inducible in Rhizobium and Agrobacterium spp. and constitutive in Bradyrhizobium spp

J Bacteriol. 1986 Jan;165(1):288-92. doi: 10.1128/jb.165.1.288-292.1986.


Protocatechuate is a universal growth substrate for members of the family Rhizobiaceae, and these bacteria utilize the aromatic compound via the beta-ketoadipate pathway. This report describes transcriptional controls exercised by different subgroups of the Rhizobiaceae over five enzymes that catalyze consecutive reactions in the pathway: protocatechuate oxygenase (EC, beta-carboxy-cis,cis-muconate lactonizing enzyme (EC, gamma-carboxymuconolactone decarboxylase (EC, beta-ketoadipate enol-lactone hydrolase (EC, and beta-ketoadipate succinyl-coenzyme A transferase (EC All five enzymes were inducible in the fast-growing strains Agrobacterium rhizogenes, Agrobacterium tumefaciens, Rhizobium fredii, Rhizobium meliloti, Rhizobium leguminosarum, and Rhizobium trifolii. Specific activities in induced cells ranged from 5- to 100-fold greater than those found in uninduced cells. In contrast to the fast-growing strains and members of every other microbial taxon examined to date, the slow-growing Bradyrhizobium japonicum and cowpea Bradyrhizobium spp. constitutively expressed four of the five enzymes; protocatechuate oxygenase was the only inducible enzyme in this group. The slow-growing strains included different DNA homology groups, so it appears likely that constitutive expression of the four enzymes is a common trait in the bradyrhizobia. This property points to the importance of aromatic compounds and aromatic catabolites in the nutrition of these organisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipates / metabolism*
  • Enzyme Induction
  • Hydroxybenzoates / metabolism
  • Rhizobiaceae / enzymology*
  • Rhizobium / enzymology*


  • Adipates
  • Hydroxybenzoates
  • 3-oxoadipic acid
  • protocatechuic acid