Purity > 90% as determined by SDS-PAGE. MW: 49.5kDa. Full Length of Mature Protein: 2-427aa. N-terminal 6xHis-tagged. Escherichia coli (strain K12). Catalyzes the hydrolytic deamination of cytosine to uracil. Is involved in the pyrimidine salvage pathway, which allows the cell to utilize cytosine for pyrimidine nucleotide synthesis. Is also able to catalyze deamination of isoguanine, a mutagenic oxidation product of adenine in DNA, and of isocytosine. To a lesser extent, also catalyzes the conversion of 5-fluorocytosine (5FC) to 5-fluorouracil (5FU); this activity allows the formation of a cytotoxic chotherapeutic agent from a non-cytotoxic precursor.