Thymidylate kinase catalyzes the phosphorylation

Phosphorylation

Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Phosphorylation activates or deactivates many protein enzymes....

 of thymidine 5'-monophosphate

Thymidine monophosphate

Thymidine monophosphate, also known as 5'-thymidylate, thymidylate, or TMP, is a nucleotide that is used as a monomer in DNA. It is an ester of phosphoric acid with the nucleoside thymidine. TMP consists of a phosphate group, the pentose sugar deoxyribose, and the nucleobase thymine...

 (dTMP) to form thymidine 5'-diphosphate (dTDP) in the presence of ATP and magnesium:

ATP + thymidine 5'-phosphate ADP + thymidine 5'-diphosphate

Thymidylate kinase is a ubiquitous enzyme of about 25 Kd and is important in the dTTP synthesis pathway for DNA synthesis. The function of dTMP kinase in eukaryotes comes from the study of a cell cycle mutant, cdc8, in Saccharomyces cerevisiae Saccharomyces cerevisiae

Saccharomyces cerevisiae

Saccharomyces cerevisiae is a species of yeast. It is perhaps the most useful yeast, having been instrumental to baking and brewing since ancient times. It is believed that it was originally isolated from the skin of grapes...

. Structural and functional analyses suggest that the cDNA codes for authentic human dTMP kinase. The mRNA levels and enzyme activities corresponded to cell cycle progression and cell growth stages.