Acireductone dioxygenase [iron(II)-requiring] () is an enzyme that catalyzes the chemical reaction
The two substrates of this enzyme are 1,2-dihydroxy-5-(methylthio)pent-1-en-3-one and oxygen. Its products are 4-(methylthio)-2-oxobutanoic acid and formic acid.
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 1,2-dihydroxy-5-(methylthio)pent-1-en-3-one:oxygen oxidoreductase (formate-forming). Other names in common use include ARD', 2-hydroxy-3-keto-5-thiomethylpent-1-ene dioxygenase (ambiguous), acireductone dioxygenase (ambiguous), E-2', and E-3 dioxygenase. It participates in the methionine salvage pathway in the bacterium Klebsiella pneumoniae.
The protein component of the enzyme is identical to that in acireductone dioxygenase (Ni2+-requiring), which uses nickel(II) rather than iron(II) as the metal at the centre of the active site.
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code .