IUBMB Enzyme Nomenclature


Accepted name: 3-hydroxy-2-methylpyridine-5-carboxylate monooxygenase

Reaction: 3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H+ + O2 = 2-(acetamidomethylidene)succinate + NAD(P)+

For diagram of reaction click here.

Other name(s): MHPCO; 3-hydroxy-2-methylpyridine-5-carboxylate,NAD(P)H:oxygen oxidoreductase (decyclizing); methylhydroxypyridinecarboxylate oxidase (misleading); 2-methyl-3-hydroxypyridine 5-carboxylic acid dioxygenase (incorrect); methylhydroxypyridine carboxylate dioxygenase (incorrect); 3-hydroxy-3-methylpyridinecarboxylate dioxygenase [incorrect]; 3-hydroxy-2-methylpyridinecarboxylate dioxygenase (incorrect)

Systematic name: 3-hydroxy-2-methylpyridine-5-carboxylate,NAD(P)H:oxygen oxidoreductase (ring-opening)

Comments: Contains FAD. The enzyme, characterized from the bacteria Pseudomonas sp. MA-1 and Mesorhizobium loti, participates in the degradation of pyridoxine (vitamin B6). Although the enzyme was initially thought to be a dioxygenase, oxygen-tracer experiments have shown that it is a monooxygenase, incorporating only one oxygen atom from molecular oxygen. The second oxygen atom that is incorporated into the product originates from a water molecule, which is regenerated during the reaction and thus does not show up in the reaction equation.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Sparrow, L.G., Ho, P.P.K., Sundaram, T.K., Zach, D., Nyns, E.J. and Snell, E.E. The bacterial oxidation of vitamin B6. VII. Purification, properties, and mechanism of action of an oxygenase which cleaves the 3-hydroxypyridine ring. J. Biol. Chem. 244 (1969) 2590-2600. [PMID: 4306031]

2. Chaiyen, P., Ballou, D.P. and Massey, V. Gene cloning, sequence analysis, and expression of 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase. Proc. Natl Acad. Sci. USA 94 (1997) 7233-7238. [PMID: 9207074]

3. Oonanant, W., Sucharitakul, J., Yuvaniyama, J. and Chaiyen, P. Crystallization and preliminary X-ray crystallographic analysis of 2-methyl-3-hydroxypyridine-5-carboxylic acid (MHPC) oxygenase from Pseudomonas sp. MA-1. Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 61 (2005) 312-314. [PMID: 16511028]

4. Yuan, B., Yokochi, N., Yoshikane, Y., Ohnishi, K. and Yagi, T. Molecular cloning, identification and characterization of 2-methyl-3-hydroxypyridine-5-carboxylic-acid-dioxygenase-coding gene from the nitrogen-fixing symbiotic bacterium Mesorhizobium loti. J. Biosci. Bioeng. 102 (2006) 504-510. [PMID: 17270714]

5. McCulloch, K.M., Mukherjee, T., Begley, T.P. and Ealick, S.E. Structure of the PLP degradative enzyme 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase from Mesorhizobium loti MAFF303099 and its mechanistic implications. Biochemistry 48 (2009) 4139-4149. [PMID: 19317437]

6. Tian, B., Tu, Y., Strid, A. and Eriksson, L.A. Hydroxylation and ring-opening mechanism of an unusual flavoprotein monooxygenase, 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase: a theoretical study. Chemistry 16 (2010) 2557-2566. [PMID: 20066695]

7. Tian, B., Strid, A. and Eriksson, L.A. Catalytic roles of active-site residues in 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase: an ONIOM/DFT study. J. Phys. Chem. B 115 (2011) 1918-1926. [PMID: 21291225]

[EC created 2018 (EC created 1972, incorporated 2018)]

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