MetaCyc Enzyme: GTP cyclohydrolase IV

Gene: mptA Accession Number: G-11168 (MetaCyc)

Synonyms: MJ0775

Species: Methanocaldococcus jannaschii

Subunit composition of GTP cyclohydrolase IV = [MptA]2
         GTP cyclohydrolase monomer = MptA

Four classes of GTP cyclohydrolases are currrently known:

GTP cyclohydrolase I converts GTP to 7,8-dihydroneopterin 3'-triphosphate, the first step in the biosynthesis of folate.

GTP cyclohydrolase II converts GTP to 2,5-diamino-6-(5-phospho-D-ribosylamino)pyrimidin-4(3H)-one, the first step in the bacterial and eukaryotic pathways for flavin biosynthesis.

GTP cyclohydrolase III converts GTP to 2-amino-5-formylamino-6-(5-phospho-D-ribosylamino)pyrimidin-4(3H)-one, the first step in the archaeal pathways for flavin biosynthesis.

GTP cyclohydrolase IV converts GTP to 7,8-dihydroneopterin 2',3'-cyclic phosphate, an early intermediate to pterins in archaea.

About This Enzyme

GTP cyclohydrolase IV from Methanocaldococcus jannaschii catalyzes the first step in the biosynthesis of methanopterin. This enzyme is the archetype of a new class of GTP cyclohydrolases that catalyzes a series of reactions most similar to that seen with GTP cyclohydrolase I, but unique in that the cyclic phosphate is the product.

The enzyme, which is a homodimer, requires Fe2+ for activity [Grochowski07].

Molecular Weight of Polypeptide: 36.263 kD (from nucleotide sequence), 37.0 kD (experimental) [Grochowski07 ]

Molecular Weight of Multimer: 84.0 kD (experimental) [Grochowski07]

Unification Links: Entrez-gene:1451652 , Protein Model Portal:Q58185 , String:243232.MJ0775 , UniProt:Q58185

Relationship Links: InterPro:IN-FAMILY:IPR003801 , InterPro:IN-FAMILY:IPR022840 , Pfam:IN-FAMILY:PF02649

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

Created 18-Mar-2009 by Caspi R , SRI International

Enzymatic reaction of: GTP cyclohydrolase IV

EC Number:

GTP + H2O <=> 7,8-dihydroneopterin 2',3'-cyclic phosphate + formate + diphosphate + H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

The reaction is favored in the direction shown.

Alternative Substrates for GTP: GDP [Grochowski07 ]

In Pathways: 6-hydroxymethyl-dihydropterin diphosphate biosynthesis II (archaea)

Cofactors or Prosthetic Groups: Fe2+ [Grochowski07]

Kinetic Parameters:

Km (μM)

pH(opt): 6.5 [Grochowski07]


Grochowski07: Grochowski LL, Xu H, Leung K, White RH (2007). "Characterization of an Fe(2+)-dependent archaeal-specific GTP cyclohydrolase, MptA, from Methanocaldococcus jannaschii." Biochemistry 46(22);6658-67. PMID: 17497938

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Tue Oct 6, 2015, biocyc13.