EC 1.5.4.1     
Accepted name: pyrimidodiazepine synthase
Reaction: 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
Glossary: 2-amino-6-acetyl-3,7,8,9-tetrahydro-3H-pyrimido[4,5-b][1,4]diazepin-4-one = pyrimidodiazepine
Other name(s): PDA synthase; pyrimidodiazepine:oxidized-glutathione oxidoreductase (ring-opening, cyclizing); pyrimidodiazepine:glutathione-disulfide oxidoreductase (ring-opening, cyclizing)
Systematic name: 2-amino-6-acetyl-3,7,8,9-tetrahydro-3H-pyrimido[4,5-b][1,4]diazepin-4-one:glutathione-disulfide oxidoreductase (ring-opening, cyclizing)
Comments: In the reverse direction, 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 formed is an acetyldihydro derivative. Involved in the formation of the eye pigment drosopterin in Drosophila melanogaster.
References:
1.  Wiederrecht, G.J. and Brown, G.M. Purification and properties of the enzymes from Drosophila melanogaster that catalyze the conversion of dihydroneopterin triphosphate to the pyrimidodiazepine precursor of the drosopterins. J. Biol. Chem. 259 (1984) 14121–14127. [PMID: 6438092]
2.  Kim, J., Suh, H., Kim, S., Kim, K., Ahn, C. and Yim, J. Identification and characteristics of the structural gene for the Drosophila eye colour mutant sepia, encoding PDA synthase, a member of the ω class glutathione S-transferases. Biochem. J. 398 (2006) 451–460. [PMID: 16712527]
[EC 1.5.4.1 created 1990, modified 2014]