In enzymology, a 3,4-dihydroxyphenylacetate 2,3-dioxygenase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are 3,4-dihydroxyphenylacetate and O<sub>2</sub>, whereas its product is 2-hydroxy-5-carboxymethylmuconate semialdehyde.
This enzyme belongs to the family of oxidoreductases, specifically those acting on single donors with O<sub>2</sub> as oxidant and incorporation of two atoms of oxygen into the substrate (oxygenases). The oxygen incorporated need not be derived from O<sub>2</sub>. The systematic name of this enzyme class is 3,4-dihydroxyphenylacetate:oxygen 2,3-oxidoreductase (decyclizing). Other names in common use include 3,4-dihydroxyphenylacetic acid 2,3-dioxygenase, HPC dioxygenase, and homoprotocatechuate 2,3-dioxygenase. This enzyme participates in tyrosine metabolism. It employs one cofactor, iron.
As of late 2007, eight structures have been solved for this class of enzymes, with PDB accession codes , , , , , , , and .