Catalyzes the FAD-dependent oxidative deamination of various amines and D-amino acids to yield the corresponding alpha-keto acids, ammonia/amine, and hydrogen peroxide. Oxidizes sarcosine (N-methylglycine), N-ethylglycine and glycine (PubMed:9827558, PubMed:11744710, PubMed:19864430). Can also oxidize the herbicide glyphosate (N-phosphonomethylglycine) (PubMed:19864430). Displays lower activities on D-alanine, D-valine, D-proline and D-methionine (PubMed:9827558, PubMed:11744710). Does not act on L-amino acids and other D-amino acids (PubMed:9827558). Is essential for thiamine biosynthesis since the oxidation of glycine catalyzed by ThiO generates the glycine imine intermediate (dehydroglycine) required for the biosynthesis of the thiazole ring of thiamine pyrophosphate (PubMed:12627963). glycine + H2O + O2 = glyoxylate + H2O2 + NH4(+) H2O + N-ethylglycine + O2 = ethylamine + glyoxylate + H2O2 H2O + O2 + sarcosine = glyoxylate + H2O2 + methylamine D-alanine + H2O + O2 = H2O2 + NH4(+) + pyruvate glyphosate + H2O + O2 = aminomethylphosphonate + glyoxylate + H(+) + H2O2 Binds 1 FAD per subunit. Is competitively inhibited by glycolate. kcat is 1.3 sec(-1) with glycine as substrate. kcat is 1.6 sec(-1) with sarcosine as substrate. kcat is 1.4 sec(-1) with N-ethylglycine as substrate. kcat is 1.3 sec(-1) with D-proline as substrate. kcat is 1.1 sec(-1) with D-alanine as substrate (at pH 8.0) (PubMed:9827558). kcat is 0.60 sec(-1) with glycine as substrate. kcat is 0.91 sec(-1) with glyphosate as substrate (at pH 8.5 and 37 degrees Celsius) (PubMed:19864430). Optimum pH is 8.0. Optimum temperature is 45 degrees Celsius. Cofactor biosynthesis; thiamine diphosphate biosynthesis. Homotetramer. Cells lacking this gene have an absolute requirement for the thiazole alcohol for growth. Introducing the gene coding for the glycine oxidase mutant Ser-51/Arg-54/Ala-244 in plants may be an effective alternative mechanism for glyphosate tolerance in transgenic crops. In addition, transgenic plants that are able to oxidize glyphosate may represent an innovative bioremediation system for the soil treated with this herbicide. Belongs to the DAO family. ThiO subfamily.