Thymidine, Pyrimidine deoxynucleoside

Supplementary information

This supplementary information is collated from multiple sources and compiled automatically.

Thymidine Kinase 1 (TK1) also known as Thymidine Kinase isoform A is an enzyme involved in the phosphorylation of thymidine into thymidine monophosphate an important component in DNA synthesis. TK1 has a molecular weight of approximately 25 kDa. It is predominantly expressed in proliferating cells with expression levels peaking during the S phase of the cell cycle. You often find TK1 in tissues with high cell division rates like bone marrow and lymphatic tissues.

Biological function summary

This enzyme is critical for DNA replication and repair by providing deoxythymidine triphosphate (dTTP) a deoxynucleoside triphosphate. TK1 operates as a monomer but can form a tetrameric complex in its active state which enhances its affinity for substrates. TK1 can process various substrates including thymidine and thymidine analogs such as 5-bromo-2'-deoxyuridine (BrdU) and EdU. These substrates are vital in molecular biology as they help in measuring DNA synthesis in cell proliferation studies.

Pathways

The function of TK1 is central to the salvage pathway of nucleotide synthesis. This pathway allows recycling of thymidine from degraded DNA which is particularly important for rapidly dividing cells that need to ensure a sufficient supply of nucleotides. TK1 acts alongside other enzymes such as thymidylate synthase and ribonucleotide reductase to maintain nucleotide balance within the cell ensuring proper DNA synthesis and cellular proliferation.

TK1 levels often increase in cancerous tissues due to their elevated cell proliferation rates. Serum TK1 is a biomarker for various cancers like leukemia and breast cancer. Studies show a correlation between high TK1 activity and tumor aggressiveness and progression. Additionally interactions of TK1 with the protein p53 a tumor suppressor show that defects in TK1 regulation can contribute to genomic instability highlighting its role in oncogenesis.