Accepted name: GTP cyclohydrolase I
Reaction: GTP + H2O = formate + 7,8-dihydroneopterin 3′-triphosphate
Glossary: 7,8-dihydroneopterin 3′-triphosphate = 6-[(1S,2R)-1,2-dihydroxy-3-triphosphooxypropyl]-7,8-dihydropterin
Other name(s): GTP cyclohydrolase; guanosine triphosphate cyclohydrolase; guanosine triphosphate 8-deformylase; dihydroneopterin triphosphate synthase; GTP 8-formylhydrolase
Systematic name: GTP 7,8-8,9-dihydrolase
Comments: The reaction involves hydrolysis of two C-N bonds and isomerization of the pentose unit; the recyclization may be non-enzymic. This enzyme is involved in the de novo synthesis of tetrahydrobiopterin from GTP, with the other enzymes involved being EC (sepiapterin reductase) and EC (6-pyruvoyltetrahydropterin synthase) [3].
1.  Burg, A.W. and Brown, G.M. The biosynthesis of folic acid. 8. Purification and properties of the enzyme that catalyzes the production of formate from carbon atom 8 of guanosine triphosphate. J. Biol. Chem. 243 (1968) 2349–2358. [PMID: 4296838]
2.  Wolf, W.A. and Brown, G.M. The biosynthesis of folic acid. X. Evidence for an Amadori rearrangement in the enzymatic formation of dihydroneopterin triphosphate from GTP. Biochim. Biophys. Acta 192 (1969) 468–478. [PMID: 4904679]
3.  Supangat, S., Choi, Y.K., Park, Y.S., Son, D., Han, C.D. and Lee, K.H. Expression, purification, crystallization and preliminary X-ray analysis of sepiapterin reductase from Chlorobium tepidum. Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 61 (2005) 202–204. [PMID: 16510994]
[EC created 1972]