1.5.4.1 2-amino-6-acetyl-3,7,8,9-tetrahydro-3H-pyrimido[4,5-b][1,4]diazepin-4-one + glutathione disulfide + H2O = 6-pyruvoyltetrahydropterin + 2 glutathione active site contains the sequence Cys-Pro-Tyr-Cys 656799 1.5.4.1 2-amino-6-acetyl-3,7,8,9-tetrahydro-3H-pyrimido[4,5-b][1,4]diazepin-4-one + glutathione disulfide + H2O = 6-pyruvoyltetrahydropterin + 2 glutathione in the reverse direction of reaction, the reduction of 6-pyruvoyl-tetrahydropterin is accompanied by the opening of the 6-membered pyrazine ring and the formation of the 7-membered diazepine ring. The pyrimidodiazepine involved is an acetyldihydro derivative. Involved in the formation of the eye pigment drosopterin in Drosophila melanogaster. -