Thymidine kinase
| Thymidine kinase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
Crystal structure of a tetramer of thymidine kinase from U. urealyticum (where the monomers are color cyan, green, red, and magenta respectively) in complex with thymidine (space-filling model, carbon = white, oxygen = red, nitrogen = blue). | |||||||||
| Identifiers | |||||||||
| EC no. | 2.7.1.21 | ||||||||
| CAS no. | 9002-06-6 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
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| Thymidine kinase | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||||
| Symbol | TK | ||||||||||
| Pfam | PF00265 | ||||||||||
| Pfam clan | CL0023 | ||||||||||
| InterPro | IPR001267 | ||||||||||
| PROSITE | PDOC00524 | ||||||||||
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| Thymidine kinase 1, soluble | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Symbol | TK1 | ||||||
| NCBI gene | 7083 | ||||||
| HGNC | 11830 | ||||||
| OMIM | 188300 | ||||||
| RefSeq | NM_003258 | ||||||
| UniProt | P04183 | ||||||
| Other data | |||||||
| EC number | 2.7.1.21 | ||||||
| Locus | Chr. 17 q23.2-25.3 | ||||||
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| Thymidine kinase 2, mitochondrial | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Symbol | TK2 | ||||||
| NCBI gene | 7084 | ||||||
| HGNC | 11831 | ||||||
| OMIM | 188250 | ||||||
| RefSeq | NM_004614 | ||||||
| UniProt | O00142 | ||||||
| Other data | |||||||
| EC number | 2.7.1.21 | ||||||
| Locus | Chr. 16 | ||||||
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Thymidine kinase is an enzyme, a phosphotransferase (a kinase): 2'-deoxythymidine kinase, ATP-thymidine 5'-phosphotransferase, EC 2.7.1.21. It can be found in most living cells. It is present in two forms in mammalian cells, TK1 and TK2. Certain viruses also have genetic information for expression of viral thymidine kinases. Thymidine kinase catalyzes the reaction:
- Thd + ATP → TMP + ADP
where Thd is (deoxy)thymidine, ATP is adenosine triphosphate, TMP is (deoxy)thymidine monophosphate and ADP is adenosine diphosphate. Thymidine kinases have a key function in the synthesis of DNA and therefore in cell division, as they are part of the unique reaction chain to introduce thymidine into the DNA. Thymidine is present in the body fluids as a result of degradation of DNA from food and from dead cells. Thymidine kinase is required for the action of many antiviral drugs. It is used to select hybridoma cell lines in production of monoclonal antibodies. In clinical chemistry it is used as a proliferation marker in the diagnosis, control of treatment and follow-up of malignant disease, mainly of hematological malignancies.