IUBMB Enzyme Nomenclature


Accepted name: GTP cyclohydrolase IV

Reaction: GTP + H2O = 7,8-dihydroneopterin 2',3'-cyclic phosphate + formate + diphosphate

For diagram of reaction click here.

Glossary: 7,8-dihydroneopterin 2',3'-cyclic phosphate = 2-amino-6-{(S)-hydroxy[(4R)-2-hydroxy-2-oxido-1,3,2-dioxaphospholan-4-yl]methyl}-7,8-dihydropteridin-4(1H)-one = 2-amino-6-[(1S,2R)-1,2,3-trihydroxypropyl]-7,8-dihydro-4(1H)-pteridinone 1,2-cyclic phosphate

Other name(s): MptA; GTP cyclohydrolase MptA

Systematic name: GTP 7,8-8,9-dihydrolase (cyclizing, formate-releasing, diphosphate-releasing)

Comments: Requires Fe2+. A zinc protein. The enzyme is involved in methanopterin biosynthesis in methanogenic archaea. cf. GTP cyclohydrolase I (EC, GTP cyclohydrolase II (EC and GTP cyclohydrolase IIa (EC

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Grochowski, L.L., Xu, H., Leung, K. and White, R.H. Characterization of an Fe2+-dependent archaeal-specific GTP cyclohydrolase, MptA, from Methanocaldococcus jannaschii. Biochemistry 46 (2007) 6658-6667. [PMID: 17497938]

[EC created 2013]

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