Thermodynamics and reduction kinetics properties of 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase.
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.
Chaiyen
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P
Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-0606, USA.
Brissette
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P
Ballou
D P
DP
Massey
V
V
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
D009525:Niacin; D006899:Mixed Function Oxygenases; C019483:methylhydroxypyridine-carboxylate dioxygenase