In enzymology, a 2,5-dihydroxypyridine 5,6-dioxygenase (EC 1.13.11.9) is an enzyme that catalyzes the chemical reaction

2,5-dihydroxypyridine + O₂ ${\displaystyle \rightleftharpoons }$ N-formylmaleamic acid

The 2 substrates of this enzyme are 2,5-dihydroxypyridine and O₂, whereas its product is N-formylmaleamic acid.^[1]

This enzyme belongs to the family of oxidoreductases, specifically those acting on single donors with O₂ as oxidant and incorporation of two atoms of oxygen into the substrate (oxygenases). The oxygen incorporated need not be derived from O₂. It employs one cofactor, iron.

This enzyme participates in nicotinate and nicotinamide metabolism.^[2]

The systematic name of this enzyme class is 2,5-dihydroxypyridine:oxygen 5,6-oxidoreductase. Other names in common use include 2,5-dihydroxypyridine oxygenase, and pyridine-2,5-diol dioxygenase.