EC - GTP cyclohydrolase I

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IntEnz Enzyme Nomenclature


Accepted name:
GTP cyclohydrolase I
Other names:
GTP 8-formylhydrolase
GTP cyclohydrolase
dihydroneopterin triphosphate synthase
guanosine triphosphate 8-deformylase
guanosine triphosphate cyclohydrolase
Systematic name:
GTP 7,8-8,9-dihydrolase



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].

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Protein domains and families: PROSITE:PDOC00672
Structural data: CSA , EC2PDB
Gene Ontology: GO:0003934
CAS Registry Number: 37289-19-3
UniProtKB/Swiss-Prot: (556) [show] [UniProt]


  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 : 2349-2358 (1968). [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 : 468-478 (1969). [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 : 202-204 (2005). [PMID: 16510994]

[EC created 1972]