Oxidase that catalyzes the oxidation of medium and long chain hydroxyacids such as 2-hydroxyhexadecanoate and 2-hydroxyoctanoate, to the correspondong 2-oxoacids. Its role in the oxidation of 2-hydroxy fatty acids may contribute to the general pathway of fatty acid alpha-oxidation. Active in vitro with the artificial electron acceptor 2,6-dichlorophenolindophenol (DCIP), but O2 is believed to be the physiological electron acceptor, leading to the production of H2O2. a (2S)-2-hydroxycarboxylate + O2 = a 2-oxocarboxylate + H2O2 2-hydroxyhexadecanoate + O2 = 2-oxohexadecanoate + H2O2 2-hydroxyoctanoate + O2 = 2-oxooctanoate + H2O2 Lipid metabolism; fatty acid metabolism. Homotetramer. Belongs to the FMN-dependent alpha-hydroxy acid dehydrogenase family.