EC - CTP synthase (glutamine hydrolyzing)

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IntEnz Enzyme Nomenclature


Accepted name:
CTP synthase (glutamine hydrolyzing)
Other names:
UTP—ammonia ligase
cytidine 5'-triphosphate synthetase
cytidine triphosphate synthetase
uridine triphosphate aminase
CTP synthetase
CTPS (gene name)
pyrG (gene name)
Systematic name:
UTP:L-glutamine amido-ligase (ADP-forming)



The enzyme contains three functionally distinct sites: an allosteric GTP-binding site, a glutaminase site where glutamine hydrolysis occurs (cf. EC, glutaminase), and the active site where CTP synthesis takes place. The reaction proceeds via phosphorylation of UTP by ATP to give an activated intermediate 4-phosphoryl UTP and ADP [4,5]. Ammonia then reacts with this intermediate generating CTP and a phosphate. The enzyme can also use ammonia from the surrounding solution [3,6].

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ERGO , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Protein domains and families: PROSITE:PDOC00405
Structural data: CSA , EC2PDB
Gene Ontology: GO:0003883
CAS Registry Number: 9023-56-7
UniProtKB/Swiss-Prot: (699) [show] [UniProt]


  1. Lieberman, I.
    Enzymatic amination of uridine triphosphate to cytidine triphosphate.
    J. Biol. Chem. 222 : 765-775 (1956). [PMID: 13367044]
  2. Long, C.W., Levitzki, A., Houston, L.L and Koshland, D.E., Jr
    Subunit structures and interactions of CTP synthetase.
    Fed. Proc. 28 : 342 (1969).
  3. Levitzki, A., Koshland, D. E.
    Ligand-induced dimer-to-tetramer transformation in cytosine triphosphate synthetase.
    Biochemistry 11 : 247-253 (1972). [PMID: 4550560]
  4. von der Saal, W., Anderson, P. M., Villafranca, J. J.
    Mechanistic investigations of Escherichia coli cytidine-5'-triphosphate synthetase. Detection of an intermediate by positional isotope exchange experiments.
    J. Biol. Chem. 260 : 14993-14997 (1985). [PMID: 2933396]
  5. Lewis, D. A., Villafranca, J. J.
    Investigation of the mechanism of CTP synthetase using rapid quench and isotope partitioning methods.
    Biochemistry 28 : 8454-8459 (1989). [PMID: 2532543]
  6. Wadskov-Hansen, S. L., Willemoes, M., Martinussen, J., Hammer, K., Neuhard, J., Larsen, S.
    Cloning and verification of the Lactococcus lactis pyrG gene and characterization of the gene product, CTP synthase.
    J. Biol. Chem. 276 : 38002-38009 (2001). [PMID: 11500486]

[EC created 1961, modified 2013]