GTP cyclohydrolase IIa

In enzymology, a GTP cyclohydrolase IIa (EC 3.5.4.29) is an enzyme that catalyzes the chemical reaction

GTP + 3 H₂O ${\displaystyle \rightleftharpoons }$ 2-amino-5-formylamino-6-(5-phosphoribosylamino)pyrimidin-4(3H)-one + 2 phosphate

GTP cyclohydrolase IIa
Identifiers
EC no.	3.5.4.29
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

Thus, the two substrates of this enzyme are GTP and H₂O, whereas its two products are 2-amino-5-formylamino-6-(5-phosphoribosylamino)pyrimidin-4(3H)-one and phosphate.

This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in cyclic amidines. The systematic name of this enzyme class is GTP 8,9-hydrolase (phosphate-forming).