title: Hydroxylation of quinaldic acid: quinaldic acid 4-monooxygenase from Alcaligenes sp. F-2 versus quinaldic acid 4-oxidoreductases.
abstract: The N-heterocycles quinaldic acid (quinoline 2-carboxylic acid), kynurenic acid (4-hydroxyquinoline 2-carboxylic acid), 2-oxo-1,2-dihydroquinoline, and xanthine are utilized by Alcaligenes sp. F-2 as sole source of carbon and energy. Although quinoline did not serve as growth substrate, 8-hydroxy-2-oxo-1,2-dihydroquinoline and 8-hydroxycoumarin, metabolites of the 'coumarin pathway' of quinoline catabolism, were isolated from the culture fluid during growth on 2-oxo-1,2-dihydroquinoline. Contrary to Serratia marcescens 2CC-1 and Pseudomonas sp. AK-2 (Sauter et al. (1993) Biol. Chem. Hoppe-Seyler 374, 1037-1046), which possess different molybdenum-containing hydroxylases catalysing the 4-hydroxylation of quinaldic acid to kynurenic acid with incorporation of oxygen derived from water and concomitant reduction of an electron acceptor, Alcaligenes sp. F-2 contains an inducible quinaldic acid 4-monooxygenase that catalyses the very same conversion in the presence of O2 and NADH. The activity of the monooxygenase was enhanced 1.5-fold by Fe2+ ions. The extremely thermolabile enzyme (apparent molecular mass: 155 kDa) exclusively accepted quinaldic acid as substrate. The 'pseudosubstrates' menadione, 8-hydroxyquinoline, and 8-hydroxy-2-oxo-1,2-dihydroquinoline effected consumption of NADH and oxygen without being hydroxylated. Quinaldic acid 4-monooxygenase was inhibited by sulfhydryl modifying and chelating agents, and by various divalent metal ions, whereas reducing agents did not affect enzymatic activity.
authors.affiliation: Institut für Mikrobiologie, Universität Hohenheim, Stuttgart, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Bubeck
authors.forename: B
authors.initials: B
authors.lastname: Tshisuaka
authors.forename: S
authors.initials: S
authors.lastname: Fetzner
authors.forename: F
authors.initials: F
authors.lastname: Lingens
mesh_terms: D000421:Alcaligenes / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D004734:Energy Metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D004795:Enzyme Stability; D005296:Ferrous Compounds / Q000494:pharmacology; D006900:Hydroxylation; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D015394:Molecular Structure; D008970:Molecular Weight; D010105:Oxygenases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011804:Quinolines / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D005296:Ferrous Compounds; D011804:Quinolines; D006899:Mixed Function Oxygenases; D010105:Oxygenases; C099749:quinaldic acid 4-monooxygenase; C082851:quinaldic acid 4-oxidoreductase; C008898:quinaldic acid