3.5.4.29: GTP cyclohydrolase IIa
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For detailed information about GTP cyclohydrolase IIa, go to the full flat file.
Reaction
Synonyms
GCH III, GTP cyclohydrolase III, MJ0145
ECTree
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Metals Ions
Metals Ions on EC 3.5.4.29 - GTP cyclohydrolase IIa
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Ca2+
calcium is detected up to 10fold in molar excess of the protein. Treatment of the protein with Chelex (Na+ form) reduces the Ca2+ to 4fold excess but does not eliminate it
CoCl2
45% of Mg2+ diphosphate phosphohydrolase activation
K+
Mg2+
Mn2+
7% of Mg2+ activation, 8% of Mg2+ diphosphate phosphohydrolase activation
Zn(OAc)2
21% of Mg2+ diphosphate phosphohydrolase activation
additional information
Mg2+
required for cyclohydrolase activity, maximal activity at 4 mM, no other metal supports full activity, maximal diphosphate phosphohydrolase activity in the presence of 5 mM MgCl2
three metal ions are located in the active site, two of which occupy positions that are analogous to those occupied by divalent metal ions in the structures of a number of palm domain containing proteins, such as DNA polymerase I. Two conserved Asp residues that coordinate the metal ions, which are also found in palm domain containing proteins, are observed in GCH III. Site-directed variants (Asp->Asn) of these residues in GCH III are less active than wild-type. The third metal ion, most likely a potassium ion, is involved in substrate recognition through coordination of O6 of GTP. The arrangement of the metal ions in the active site suggests that GCH III utilizes two metal ion catalysis
additional information
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three metal ions are located in the active site, two of which occupy positions that are analogous to those occupied by divalent metal ions in the structures of a number of palm domain containing proteins, such as DNA polymerase I. Two conserved Asp residues that coordinate the metal ions, which are also found in palm domain containing proteins, are observed in GCH III. Site-directed variants (Asp->Asn) of these residues in GCH III are less active than wild-type. The third metal ion, most likely a potassium ion, is involved in substrate recognition through coordination of O6 of GTP. The arrangement of the metal ions in the active site suggests that GCH III utilizes two metal ion catalysis