Description
Thymidine kinase 1, soluble (gene name TK1), is a human thymidine kinase. Thymidine kinase catalyzes the phosphorylation of thymidine to deoxythymidine monophosphate. This gene is mapped to 17q23.2-q25.3. It is estimated that the maximal size of the TK1 gene is 14 kb and its minimal size between 4 and 5 kb. The gene contains many noncoding inserts and numerous Alu sequences. There are two forms of this protein, which have been identified in animal cells, one in cytosol and one in mitochondria. Activity of the cytosolic enzyme is high in proliferating cells and peaks during the S-phase of the cell cycle; it is very low in resting cells