Cytidine deaminase is an enzyme that catalyzes the conversion of cytidine to uridine by removing an amino group. This process is essential in the metabolism of nucleotides, which are the building blocks of DNA and RNA. By facilitating this conversion, cytidine deaminase plays a crucial role in regulating the levels of nucleotides in cells. This enzyme is also significant in pharmacology, particularly in the metabolism of certain antiviral and anticancer drugs. For example, it can influence the effectiveness of medications like azacitidine and gemcitabine, which are used in treating various cancers. Understanding cytidine deaminase can help improve therapeutic strategies.