In enzymology, a 3-hydroxy-2-methylpyridinecarboxylate dioxygenase (EC 1.14.12.4) is an enzyme that catalyzes the chemical reaction

3-hydroxy-2-methylpyridine-5-carboxylate + NAD(P)H + H⁺ + O₂ ${\displaystyle \rightleftharpoons }$ 2-(acetamidomethylene)succinate + NAD(P)+

The 5 substrates of this enzyme are 3-hydroxy-2-methylpyridine-5-carboxylate, NADH, NADPH, H⁺, and O₂, whereas its 3 products are 2-(acetamidomethylene)succinate, NAD⁺, and NADP⁺.

This enzyme belongs to the family of oxidoreductases, specifically those acting on paired donors, with O₂ as oxidant and incorporation or reduction of oxygen. The oxygen incorporated need not be derived from O₂ with NADH or NADPH as one donor, and incorporation of two atoms of oxygen into the other donor. The systematic name of this enzyme class is 3-hydroxy-2-methylpyridine-5-carboxylate,NAD(P)H:oxygen oxidoreductase (decyclizing). Other names in common use include methylhydroxypyridinecarboxylate oxidase, 2-methyl-3-hydroxypyridine 5-carboxylic acid dioxygenase, methylhydroxypyridine carboxylate dioxygenase, and 3-hydroxy-3-methylpyridinecarboxylate dioxygenase [incorrect]. This enzyme participates in vitamin B₆ metabolism. It employs one cofactor, FAD.

• Sparrow LG, Ho PP, Sundaram TK, Zach D, Nyns EJ, Snell EE (1969). "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 (10): 2590–600. doi:10.1016/S0021-9258(18)83441-X. PMID 4306031.