|Gene:||mptA||Accession Number: G-11168 (MetaCyc)|
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 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.
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]
Enzymatic reaction of: GTP cyclohydrolase IV
EC Number: 188.8.131.52
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.
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
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