Idoxuridine, Antiviral thymidine analog

Supplementary information

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

Thymidine Kinase 1 also known as TK1 is a cellular enzyme that plays an important role in the pyrimidine salvage pathway by converting deoxythymidine into thymidine monophosphate which is a precursor for DNA synthesis. The molecular mass of human TK1 is approximately 25 kDa. TK1 expression mainly occurs in the cytosol of actively dividing cells particularly during the S-phase of the cell cycle. The enzyme shows increased activity in proliferating tissues and tumors which makes it a useful marker for cell proliferation.

Biological function summary

Thymidine kinase 1 contributes to DNA replication by supplying thymidine for nucleotide excision repair and synthesis. It acts independently rather than as part of a larger complex. TK1 is especially important in rapidly dividing cells like those in bone marrow and embryonic tissues where DNA synthesis is critical. Its activity provides cells the ability to use exogenous nucleoside sources enhancing their proliferation capabilities and adaptability in various physiological and pathological conditions.

Pathways

TK1 plays a notable part in the nucleotide salvage pathway and the cell cycle regulation pathway. In the nucleotide salvage pathway TK1 helps recycle thymidine ensuring a supply of thymidine triphosphate for DNA synthesis and repair. This is important for balancing DNA replication needs especially when the de novo synthesis pathway is less efficient. In the cell cycle regulation pathway TK1 activity correlates with proteins like cyclin-dependent kinases reflecting the enzyme's role in regulating cell division and growth.

TK1 levels show a strong relationship with cancer and autoimmune diseases. Elevated TK1 activity is often seen in malignancies such as leukemia and lymphoma where rapid cell division is a hallmark. In autoimmune disorders like rheumatoid arthritis dysregulated cell turnover can affect immune cell proliferation potentially involving changes in TK1 expression. The enzyme interacts with proteins involved in these diseases such as tumor-associated antigens which can drive abnormal cell growth and proliferation.