ribonucleoside-diphosphate reductase activity
Definition
Target type: molecularfunction
Catalysis of the formation of 2'-deoxyribonucleoside diphosphate from ribonucleoside diphosphate, using either thioredoxin disulfide or glutaredoxin disulfide as an acceptor. [GOC:dph, GOC:vw, PMID:16756507]
Ribonucleoside-diphosphate reductase (RNR) activity is a crucial enzymatic function that catalyzes the reduction of ribonucleotides to deoxyribonucleotides, a fundamental step in DNA synthesis. This process is essential for the replication and repair of DNA, as well as for the production of precursors for other essential biomolecules.
RNRs are multimeric enzymes consisting of two subunits: a protein subunit (R1) and a radical-generating subunit (R2). The R1 subunit contains the catalytic site where the reduction of ribonucleotides takes place, while the R2 subunit generates a stable tyrosyl radical that is essential for the enzymatic reaction.
The catalytic cycle of RNR begins with the binding of a ribonucleotide substrate to the R1 subunit. The substrate is then activated by the tyrosyl radical generated in the R2 subunit, which initiates a series of electron transfer reactions. These reactions involve the transfer of electrons from a reduced flavin cofactor in the R1 subunit to the substrate, ultimately leading to the reduction of the 2'-hydroxyl group of the ribonucleotide to a hydrogen atom, forming the corresponding deoxyribonucleotide.
The RNR reaction requires a reducing agent, typically NADPH, to provide the electrons necessary for the reduction process. Additionally, RNRs are highly regulated enzymes, ensuring that the production of deoxyribonucleotides is coordinated with cellular demands for DNA synthesis. This regulation involves various mechanisms, including allosteric control by the levels of deoxyribonucleotides and effector molecules, as well as the modulation of enzyme activity by specific protein kinases.
In summary, ribonucleoside-diphosphate reductase activity is a critical molecular function that plays a central role in DNA synthesis and cellular proliferation. It is a complex enzymatic process involving multiple steps, cofactors, and regulatory mechanisms that ensure the precise control of deoxyribonucleotide production, ultimately supporting the integrity and maintenance of the genome.'
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Proteins (1)
| Protein | Definition | Taxonomy |
|---|---|---|
| Ribonucleoside-diphosphate reductase large subunit | A ribonucleoside-diphosphate reductase large subunit that is encoded in the genome of human. [PRO:DNx, UniProtKB:P23921] | Homo sapiens (human) |
Compounds (4)
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| hydroxyurea | one-carbon compound; ureas | antimetabolite; antimitotic; antineoplastic agent; DNA synthesis inhibitor; EC 1.17.4.1 (ribonucleoside-diphosphate reductase) inhibitor; genotoxin; immunomodulator; radical scavenger; teratogenic agent | |
| uridine diphosphate | Uridine Diphosphate: A uracil nucleotide containing a pyrophosphate group esterified to C5 of the sugar moiety. | pyrimidine ribonucleoside 5'-diphosphate; uridine 5'-phosphate | Escherichia coli metabolite; mouse metabolite |
| cytidine diphosphate | Cytidine Diphosphate: Cytidine 5'-(trihydrogen diphosphate). A cytosine nucleotide containing two phosphate groups esterified to the sugar moiety. Synonyms: CRPP; cytidine pyrophosphate. | cytidine 5'-phosphate; pyrimidine ribonucleoside 5'-diphosphate | Escherichia coli metabolite; mouse metabolite |
| 1-aminoadenosine | 1-aminoadenosine: structure |