DNA polymerase, DNA, Ribonucleotide reductase

The target entry "DNA polymerase, DNA, Ribonucleotide reductase" is incorrect as it improperly combines two distinct and critical enzymes: DNA polymerase and Ribonucleotide reductase, and includes a redundant 'DNA' term. Each should be treated as a separate entity for accurate data representation. **DNA polymerase** is an essential enzyme that catalyzes the synthesis of DNA from deoxyribonucleoside triphosphates during DNA replication and repair. It works by copying a DNA template strand and extending the 3' end of a growing DNA chain, ensuring fidelity through proofreading abilities. Aliases for DNA polymerase include: DNA-directed DNA polymerase. Different classes exist in prokaryotes and eukaryotes, specialized for replication, repair, or mitochondrial DNA synthesis. **Ribonucleotide reductase (RNR)** is the enzyme responsible for the conversion of ribonucleotides to deoxyribonucleotides, the building blocks needed for DNA synthesis. It is a rate-limiting and tightly regulated enzyme, employing radical chemistry to mediate the reduction reaction and functioning as a key control point for the balance of dNTP pools during the cell cycle. Aliases for Ribonucleotide reductase include: RNR, ribonucleoside diphosphate reductase. Its activity is allosterically regulated and essential for both DNA replication and repair. RNR is a major target for cytostatic drugs in oncology and virology due to its pivotal role in nucleic acid metabolism.

Drugs targeting DNA polymerase, such as nucleoside/nucleotide analogs, act as chain terminators upon incorporation into DNA, leading to faulty DNA synthesis; some also function as competitive inhibitors of the dNTP binding site. Drugs targeting Ribonucleotide reductase typically inhibit the enzyme by quenching its catalytic radical or chelating the essential metal ion, thereby preventing the reduction of ribonucleotides to deoxyribonucleotides. This action leads to a depletion of dNTPs and subsequent inhibition of DNA synthesis.