title: Thermodynamics and reduction kinetics properties of 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase.
abstract: The investigation by absorbance and fluorescence rapid reaction spectrophotometry of the binding of the substrate MHPC (2-methyl-3-hydroxypyridine-5-carboxylic acid) or the substrate analog 5HN (5-hydroxynicotinic acid) to the flavoprotein MHPCO (2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase) shows that the binding proceeds in two steps. An enzyme-substrate complex initially formed is followed by a ligand-induced isomerization. This binding process is required for efficient reduction of the enzyme-bound flavin, as evidenced by the fact that MHPCO-substrate complexes can be reduced by NADH much faster than the enzyme alone. Since redox potential values of MHPCO and MHPCO-substrate complexes are the same, steric factors, such as the relative orientation of MHPC to the enzyme-bound flavin, are important for efficient hydride transfer to occur.
authors.affiliation: Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-0606, USA.
authors.forename: P
authors.initials: P
authors.lastname: Chaiyen
authors.forename: P
authors.initials: P
authors.lastname: Brissette
authors.forename: D P
authors.initials: DP
authors.lastname: Ballou
authors.forename: V
authors.initials: V
authors.lastname: Massey
mesh_terms: D001665:Binding Sites; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000378:metabolism*; D009525:Niacin / Q000737:chemistry; D010084:Oxidation-Reduction; D011549:Pseudomonas / Q000201:enzymology; D013379:Substrate Specificity
chemical_list: D009525:Niacin; D006899:Mixed Function Oxygenases; C019483:methylhydroxypyridine-carboxylate dioxygenase