title: Catabolism of isonicotinate by Mycobacterium sp. INA1: extended description of the pathway and purification of the molybdoenzyme isonicotinate dehydrogenase.
abstract: 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.
authors.affiliation: Institut für Mikrobiologie, Universität Göttingen, FRG.
authors.forename: A
authors.initials: A
authors.lastname: Kretzer
authors.forename: K
authors.initials: K
authors.lastname: Frunzke
authors.forename: J R
authors.initials: JR
authors.lastname: Andreesen
mesh_terms: D000595:Amino Acid Sequence; D007539:Isonicotinic Acids / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D009161:Mycobacterium / Q000378:metabolism*; D010084:Oxidation-Reduction; D014233:Tricarboxylic Acids / Q000378:metabolism
chemical_list: D007539:Isonicotinic Acids; D014233:Tricarboxylic Acids; D006899:Mixed Function Oxygenases; C024738:isonicotinic acid hydroxylase; C028021:tricarballylic acid