Catalyzes the oxidation of glycolate to glyoxylate, with a reduction of O2 to H2O2 (By similarity). Is a key enzyme in photorespiration in plants (By similarity). Can exert a strong regulation over photosynthesis, possibly through a feed-back inhibition on Rubisco activase. Does not seem to play a role in oxalate accumulation (By similarity). glycolate + O2 = glyoxylate + H2O2 Photosynthesis; photorespiration; glycine from 2-phosphoglycolate: step 2/3. Homotetramer (By similarity). Interacts with rice dwarf virus (RDV) P8. This interaction promotes viral P8 relocation to virus factories peripheral to peroxisomes (By similarity). Belongs to the FMN-dependent alpha-hydroxy acid dehydrogenase family.