ISSN:
0570-0833
Keywords:
Ribonucleotides
;
Nucleotides
;
Biosynthesis
;
Enzymes
;
Deoxyribonucleotides
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Ribonucleotide reductases are enzymes that synthesize the deoxyribonucleotides required for the replication of DNA in dividing cells. They thus have a key function for the growth of microorganisms and of all plant and animal tissues. The enzymes reduce all four purine and pyrimidine ribonucleotides (as the 5′-diphosphates or triphosphates) with direct substitution of the 2′-hydroxyl group by hydrogen. The physiological reducing agents are the mercapto groups of thioredoxins, a group of small proteins, which are regenerated from the oxidized form by NADPH-dependent thioredoxin reductases. There are two known types of ribonucleotide reductases (I and II), which catalyze hydrogen transfer with the aid of protein-bound iron ions or of 5′-deoxyadenosylcobalamin (coenzyme B12); free radicals can be detected in both cases. The enzymes are regulated by effector nucleotides. There may exist a homeostatic mechanism, which guarantees the supply of DNA precursors to the cell.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/anie.197405691
