Catalyzes the FAD-dependent oxidative deamination of glycine. 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. Catalyzes the rearrangement of 1-deoxy-D-xylulose 5-phosphate (DXP) to produce the thiazole phosphate moiety of thiamine. Sulfur is provided by the thiocarboxylate moiety of the carrier protein ThiS. In vitro, sulfur can be provided by H(2)S. glycine + H2O + O2 = glyoxylate + H2O2 + NH4(+) 1-deoxy-D-xylulose 5-phosphate + 2-iminoacetate + [sulfur-carrier protein ThiS]-C-terminal Gly-NH-CH2-C(O)SH = 2-[(2R,5Z)-2-carboxy-4-methylthiazol-5(2H)-ylidene]ethyl phosphate + [sulfur-carrier protein ThiS]-C-terminal Gly-Gly + 2 H(+) + 2 H2O Cofactor biosynthesis; thiamine diphosphate biosynthesis. Interacts with ThiH and ThiS. In the N-terminal section; belongs to the DAO family. ThiO subfamily. In the C-terminal section; belongs to the ThiG family.