Catabolism of isonicotinate by Mycobacterium sp. INA1: extended description of the pathway and purification of the molybdoenzyme isonicotinate dehydrogenase

J Gen Microbiol. 1993 Nov;139(11):2763-72. doi: 10.1099/00221287-139-11-2763.


Catabolism of isonicotinate by Mycobacterium sp. INA1 has been shown to proceed via 2-hydroxyisonicotinate, 2,6-dihydroxyisonicotinate (citrazinate), citrazyl-CoA and 2,6-dioxopiperidine-4-carboxyl-CoA. An extended pathway involving propane-1,2,3-tricarboxylate as a further intermediate is presented in this paper. Propane-1,2,3-tricarboxylate was oxidized stepwise to 2-oxoglutarate involving an oxidase, aconitase and isocitrate dehydrogenase. Isonicotinate dehydrogenase catalyses the first step of isonicotinate metabolism in Mycobacterium sp. INA1. The enzyme was purified to apparent homogeneity by a three-step procedure. Enrichment was accompanied by partial loss in specific activity. The native enzyme had a molecular mass of either 125 kDa or 250 kDa, when estimated by native gradient PAGE or gel filtration, respectively. SDS-gel electrophoresis revealed three types of subunits with molecular masses of approximately 83, 31 and 19 kDa. N-Terminal amino acid sequences of all three subunits have been determined. Molybdenum, iron, acid-labile sulphur and FAD were present at molar ratios of 1, 4, 4, 1 per protomer (125 kDa). The molybdenum-complexing cofactor was shown to be molybdopterin cytosine dinucleotide. Besides isonicotinate, only quinoline-4-carboxylate was found to be oxidized at appreciable rates.

MeSH terms

  • Amino Acid Sequence
  • Isonicotinic Acids / metabolism*
  • Mixed Function Oxygenases / chemistry
  • Mixed Function Oxygenases / isolation & purification
  • Mixed Function Oxygenases / metabolism*
  • Molecular Sequence Data
  • Mycobacterium / metabolism*
  • Oxidation-Reduction
  • Tricarboxylic Acids / metabolism


  • Isonicotinic Acids
  • Tricarboxylic Acids
  • Mixed Function Oxygenases
  • isonicotinic acid hydroxylase
  • tricarballylic acid