Ribonukleotidireduktaasissa

Ribonucleotide reductase (RNR) is an enzyme complex that catalyzes the reduction of ribonucleotides to deoxyribonucleotides, a crucial step in DNA synthesis. This process is essential for DNA replication and repair, as well as for the synthesis of deoxyribonucleotides required for DNA and RNA synthesis. RNR is found in all living organisms, from bacteria to humans, and plays a vital role in maintaining genomic stability.

The RNR complex consists of two subunits: R1 and R2. The R1 subunit contains the catalytic site and is responsible for the reduction of ribonucleotides to deoxyribonucleotides. The R2 subunit is a homodimer that binds to the R1 subunit and provides structural stability to the complex. The R2 subunit also contains a thioredoxin-like domain that is involved in the regulation of RNR activity.

RNR activity is regulated by several mechanisms, including feedback inhibition by deoxyribonucleotides, allosteric regulation by nucleotides, and post-translational modification. In addition, RNR is subject to transcriptional and translational regulation, as well as to proteasome-mediated degradation.

RNR is a target for several anticancer drugs, including the antimetabolites 5-fluorouracil and capecitabine, as well as the topoisomerase inhibitors etoposide and teniposide. These drugs inhibit RNR activity, leading to the depletion of deoxyribonucleotides and the induction of apoptosis in cancer cells.

In summary, ribonucleotide reductase is a critical enzyme complex that plays a central role in DNA synthesis and repair. Its activity is tightly regulated by various mechanisms, and it is a target for several anticancer drugs. Understanding the structure, function, and regulation of RNR is essential for the development of new therapeutic strategies for cancer and other genetic disorders.