Broad substrate specificity (S)-2-hydroxy-acid oxidase that preferentially oxidizes glycolate (PubMed:10777549, PubMed:17669354, PubMed:18215067, PubMed:10978532). The glyoxylate produced by the oxidation of glycolate can then be utilized by alanine-glyoxylate aminotransferase for the peroxisomal synthesis of glycine; this pathway appears to be an important step for the detoxification of glyoxylate which, if allowed to accumulate, may be metabolized to oxalate with formation of kidney stones (PubMed:10978532, PubMed:17669354). Can also catalyze the oxidation of glyoxylate, and long chain hydroxyacids such as 2-hydroxyhexadecanoate and 2-hydroxyoctanoate, albeit with much lower catalytic efficiency (PubMed:10777549, PubMed:17669354, PubMed:18215067). 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 (PubMed:10777549, PubMed:17669354, PubMed:18215067, PubMed:10978532). Is not active on L-lactate and 2-hydroxybutanoate (PubMed:10777549). a (2S)-2-hydroxycarboxylate + O2 = a 2-oxocarboxylate + H2O2 glycolate + O2 = glyoxylate + H2O2 glyoxylate + H2O + O2 = H(+) + H2O2 + oxalate 2-hydroxyhexadecanoate + O2 = 2-oxohexadecanoate + H2O2 2-hydroxyoctanoate + O2 = 2-oxooctanoate + H2O2 Inhibited by its product oxalate (PubMed:17669354). Inhibited by high concentrations of dichlorophenolindophenol (DCIP) in vitro (PubMed:17669354). kcat is 3.6 sec(-1) for the oxidation of glycolate with DCIP as electron acceptor (at pH 7.0 and 37 degrees Celsius) (PubMed:17669354). kcat is 4.1 sec(-1) for the oxidation of glycolate with DCIP as electron acceptor (at pH 7.5 and 37 degrees Celsius) (PubMed:18215067). kcat is 0.7 sec(-1) for the oxidation of glyoxylate with DCIP as electron acceptor (at pH 7.5 and 37 degrees Celsius) (PubMed:18215067). kcat is 0.83 sec(-1) for the oxidation of glyoxylate with DCIP as electron acceptor (at pH 7.0 and 37 degrees Celsius) (PubMed:17669354). kcat is 0.46 sec(-1) for the oxidation of L-lactate with DCIP as electron acceptor (at pH 7.0 and 37 degrees Celsius) (PubMed:17669354). kcat is 0.11 sec(-1) for the oxidation of L-mandelate with DCIP as electron acceptor (at pH 7.0 and 37 degrees Celsius) (PubMed:17669354). Shows a higher catalytic efficiency for glycolate compared to glyoxylate (PubMed:17669354, PubMed:18215067). Amino-acid biosynthesis; glycine biosynthesis. Homotetramer. Highly expressed in liver. Belongs to the FMN-dependent alpha-hydroxy acid dehydrogenase family.