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EC 3.5.4.25 Details
show Brenda entryEC number
3.5.4.25
Accepted name
GTP cyclohydrolase II
Reaction
GTP + 4 H2O = formate + 2,5-diamino-6-hydroxy-4-(5-phospho-D-ribosylamino)pyrimidine + 2 phosphate
Other name(s)
guanosine triphosphate cyclohydrolase II,
GTP-8-formylhydrolase,
ribA (gene name),
GTP 7,8-8,9-dihydrolase (diphosphate-forming)
Systematic name
GTP 7,8-8,9-dihydrolase (formate-releasing, phosphate-releasing)
CAS registry number
56214-35-8
Comment
The enzyme, found in prokaryotes and some eukaryotes, hydrolytically cleaves the C-N bond at positions 8 and 9 of GTP guanine, followed by a subsequent hydrolytic attack at the base, which liberates formate, and cleavage of the α-β phosphodiester bond of the triphosphate to form diphosphate. The enzyme continues with a slow cleavage of the diphosphate to form two phosphate ions. The enzyme requires zinc and magnesium ions for the cleavage reactions at the GTP guanine and triphosphate sites, respectively. It is one of the enzymes required for flavin biosynthesis in many bacterial species, lower eukaryotes, and plants. cf. EC 3.5.4.16, GTP cyclohydrolase I, EC 3.5.4.29, GTP cyclohydrolase IIa, and EC 3.5.4.39, GTP cyclohydrolase IV.
History
created 1984, modified 2011, modified 2022
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1 Oxidoreductases
1.1 Acting on the CH-OH group of donors
3.5.4.1 cytosine deaminase
