Isocytosine (iC)

Isocytosine is a pyrimidine base and a structural isomer of the naturally occurring nucleobase cytosine (PubChem CID 67531). It is chemically defined as 2-aminopyrimidin-4(1H)-one and is primarily recognized for its role in synthetic biology, where it serves as a component of expanded genetic alphabets (Wikipedia). In these artificial systems, isocytosine forms a stable base pair with isoguanine via three hydrogen bonds, distinct from the standard Watson-Crick base pairs (PubMed: 30792298). Because it is a small molecule building block rather than a protein such as an enzyme or receptor, isocytosine is not classified as a therapeutic target. There are currently no approved drugs or clinical candidates designed to modulate isocytosine, and it does not have a known direct role in the pathophysiology of human diseases. It is occasionally used in chemical research to study the tautomerism and hydrogen-bonding patterns of nucleic acid analogs. In some bacterial species, enzymes like isocytosine deaminase have been identified, which catalyze the conversion of isocytosine to uracil, but these are not targets for human medicine.

Other names

2-Aminopyrimidin-4(1H)-one2-Amino-4-hydroxypyrimidine2-Amino-4-oxopyrimidine2-Aminopyrimidin-4-olPseudocytosine

Not applicable as isocytosine is a small molecule nucleobase and not a therapeutic target protein.