DTYMK (deoxythymidylate kinase (thymidylate kinase)), also known as CDC8, TMPK, TYMK or dTMP kinase, is a 212 amino acid protein that belongs to the thymidylate kinase family and is involved in pyrimidine metabolism. Specifically, DTYMK catalyzes the ATP-dependent conversion of dTMP (deoxythymidine monophosphate) to dTDP (deoxythymidine diphosphate), which then functions as one of the four nucleotides in DNA. Via its role in the catalytic creation of dTDP, DTYMK plays an important role in the pathway of DNA synthesis and is thought to be involved in cell cycle progression and cell growth. DTYMK expression levels peak during the S phase (synthesis phase) of the cell cycle, further supporting the role of DTYMK in DNA synthesis.