Cytidine vs. Cytosine: Structure, Function, and Uses

Structure

Cytidine is a pyrimidine nucleoside formed by linking cytosine to a ribose ring (ribofuranose) via a β-N1-glycosidic bond. Cytosine is one of the five nitrogenous bases that make up nucleic acids, along with thymine, uracil, adenine, and guanine. Cytidine appears as a white crystalline powder with a melting point of 230 °C, much lower than cytosine, and a high solubility in water. Cytosine, whose IUPAC name is 6-amino-1H-pyrimidin-2-one, contains a single heterocyclic aromatic ring, a keto group at C2, and an amine group at C4. The molecule is planar in shape and has high boiling and melting points.

Function

Cytidine is an essential component of RNA. It is also a precursor to uridine, which is also used in RNA synthesis. In addition to its role in RNA, cytidine is also essential for glutamate cycling and glutamate/glutamine levels in the brain. Cytosine is mainly used as a nitrogenous base in DNA and RNA, combining with guanine to form base pairs and the genetic code in DNA and RNA. Cytosine can also act as an enzyme cofactor when combined with three phosphate groups to form the energy carrier CTP.

Uses

Cytidine combined with uridine can be used to treat neuropsychiatric deficits associated with cerebrovascular disease. Cytidine is also a potential antidepressant, and cytidine analogs are often used in cancer chemotherapy. As a key component of nucleic acid composition, cytosine plays a vital role in genetics, cell function and biological reactions. It is often used in the field of epigenetics to study the role of DNA modification in controlling gene expression in organisms. In the field of medicine, cytosine can be used to prepare antifungal and antiviral drugs.

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