Cytosine deaminase

Cytosine deaminase
cytosine deaminase
EC number
CAS number 9025-05-2
IntEnz IntEnz view
ExPASy NiceZyme view
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO

In enzymology, a cytosine deaminase (EC is an enzyme that catalyzes the chemical reaction

cytosine + H2O \rightleftharpoons uracil + NH3

Thus, the two substrates of this enzyme are cytosine and H2O, whereas its two products are uracil and NH3.

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 cytosine aminohydrolase. This enzyme is also called isocytosine deaminase. This enzyme participates in pyrimidine metabolism.

Structural studies

As of late 2007, 13 structures have been solved for this class of enzymes, with PDB accession codes 1K6W, 1K70, 1OX7, 1P6O, 1R9X, 1R9Y, 1RA0, 1RA5, 1RAK, 1RB7, 1UAQ, 1YSB, and 1YSD.


  • COHEN SS, BARNER HD (1957). "The conversion of 5-methyldeoxycytidine to thymidine in vitro and in vivo". J. Biol. Chem. 226 (2): 631–42. PMID 13438848. 
  • Kream J and Chargaff E (1952). "On the cytosine deaminase of yeast". J. Am. Chem. Soc. 74 (20): 5157–5160. doi:10.1021/ja01140a050.