Quinoline 2-oxidoreductase and 2-oxo-1,2-dihydroquinoline 5,6-dioxygenase from Comamonas testosteroni 63. The first two enzymes in quinoline and 3-methylquinoline degradation

Eur J Biochem. 1995 Sep 1;232(2):536-44. doi: 10.1111/j.1432-1033.1995.tb20841.x.


The enzymes catalysing the first two steps of quinoline and 3-methylquinoline degradation by Comamonas testosteroni 63 were investigated. Quinoline 2-oxidoreductase, which catalyses the hydroxylation of (3-methyl-)quinoline to (3-methyl-)2-oxo-1,2-dihydroquinoline, was purified to apparent homogeneity. The native enzyme, with a molecular mass of 360 kDa, is composed of three non-identical subunits (87, 32, and 22 kDa), occurring in a ratio of 1.16:1:0.83. Containing FAD, molybdenum, iron, and acid-labile sulfur in the stoichiometric ratio of 2:2:8:8, the enzyme belongs to the molybdo-iron/sulfur flavoproteins. Molybdopterin cytosine dinucleotide is the organic part of the pterin molybdenum cofactor. Comparison of N-terminal amino acid sequences revealed similarities to a number of procaryotic molybdenum-containing hydroxylases. Especially the N-termini of the beta-subunits of the quinoline 2-oxidoreductases from Comamonas testosteroni 63, Pseudomonas putida 86, and Rhodococcus spec. B1, and of quinoline-4-carboxylic acid 2-oxidoreductase from Agrobacterium spec. 1B showed striking similarities. Further degradation of (3-methyl-)2-oxo-1,2-dihydroquinoline proceeds via dioxygenation at the benzene ring, i.e. at 5,6-position [Schach, S., Schwarz, G., Fetzner, S. & Lingens, F. (1993) Biol. Chem. Hoppe-Seyler 374, 175-181]. 2-Oxo-1,2-dihydroquinoline 5,6-dioxygenase was partially purified; NADH and oxygen are required for the reaction, and the enzymic activity is enhanced 1.5-fold by addition of Fe2+ ions. Unexpectedly, this aromatic ring dioxygenase did not separate into distinct protein components, but is apparently a single-component enzyme. The molecular mass was estimated to be about 260 kDa. 2-Oxo-1,2-dihydroquinoline 5,6-dioxygenase is very thermolabile. However, dithioerythritol and low concentrations of substrate had a moderately stabilizing effect. 2-Oxo-1,2-dihydroquinoline 5,6-dioxygenase is inhibited by sulfhydryl-blocking agents, by metal-chelating agents, and by the flavin analogues quinacrine and acriflavin.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Biodegradation, Environmental
  • Enzyme Stability
  • Gram-Negative Aerobic Bacteria / enzymology*
  • Gram-Negative Aerobic Bacteria / genetics
  • Molecular Sequence Data
  • Molecular Weight
  • Oxidoreductases / chemistry
  • Oxidoreductases / genetics
  • Oxidoreductases / metabolism*
  • Oxidoreductases Acting on CH-CH Group Donors*
  • Oxygenases / chemistry
  • Oxygenases / genetics
  • Oxygenases / metabolism*
  • Protein Conformation
  • Quinolines / metabolism
  • Sequence Homology, Amino Acid
  • Spectrophotometry
  • Substrate Specificity


  • Quinolines
  • 3-methylquinoline
  • quinoline
  • Oxidoreductases
  • Oxygenases
  • 2-oxo-1,2-dihydroquinoline 5,6-dioxygenase
  • Oxidoreductases Acting on CH-CH Group Donors
  • quinoline 2-oxidoreductase

Associated data

  • SWISSPROT/P80464
  • SWISSPROT/P80465
  • SWISSPROT/P80466