Galactose oxidase
![](/Images/godic/202501/14/1gog5326.jpg")
![Active site structure of galactose oxidase with coordinating ligands shown. The indole ring of Trp290 forms a](/Images/godic/202501/14/Active_site_of_Galactose_Oxidase5326.jpg")
![](/Images/godic/202501/14/The_redox_scheme_and_the_oxidation_states_of_galactose_oxidase5326.png")
![](/Images/godic/202501/14/Mechanism_of_Galactose_Oxidase5326.jpg")
Galactose oxidase (D-galactose:oxygen 6-oxidoreductase, D-galactose oxidase, beta-galactose oxidase; abbreviated GAO, GAOX, GOase; EC1.1.3.9) is an enzyme that catalyzes the oxidation of D-galactose in some species of fungi.
Galactose oxidase belongs to the family of oxidoreductases. Copper ion is required as a cofactor for galactose oxidase. A remarkable feature of galactose oxidase is that it is a free radical enzyme. Its catalytic site contains a free radical ligand coordinating to the copper center. This free radical ligand is a covalently cross-linked cysteine and tyrosine side chains that is formed during post-translational modification.