InterPro domain: IPR002125

Cytidine deaminase (EC 3.5.4.5) (cytidine aminohydrolase) catalyses thehydrolysis of cytidine into uridine and ammonia while deoxycytidylatedeaminase (EC 3.5.4.12) (dCMP deaminase) hydrolyses dCMP into dUMP. Bothenzymes are known to bind zinc and to require it for their catalytic activity[ 1 , 2 ]. The deaminases possess either one or two conserved zinc-coordinating (Z) motifs, with the consensus amino acid signature H-x(1)-E-x(24,28)-P-C-x(2,4)-C. This motif is required for catalytic activity. Zinc coordination is mediated by a histidine and two cysteines [ 3 ]. The CMP/dCMP-type deaminase domain consists of a central beta-sheet with one or more alpha helices on each side [ 4 ].

This entry represents the CMP/dCMP-type deaminase domain. Some enzymes, such as riboflavin biosynthesis protein PYRR, have a non-functional deaminase domain that lacks the catalytically essential zinc-binding residues [ 5 ].

1. Cloning and nucleotide sequence of the Escherichia coli cytidine deaminase (ccd) gene. Biochemistry 31, 4168-74
2. T4-phage deoxycytidylate deaminase is a metalloprotein containing two zinc atoms per subunit. J. Biol. Chem. 268, 2288-91
3. Crystal structure of the APOBEC3G catalytic domain reveals potential oligomerization interfaces. Structure 18, 28-38
4. Crystal structure of the tetrameric cytidine deaminase from Bacillus subtilis at 2.0 A resolution. Biochemistry 41, 2563-70
5. Identification and characterization of the missing pyrimidine reductase in the plant riboflavin biosynthesis pathway. Plant Physiol. 161, 48-56