title: Continual presence of oxygen and iron required for mammalian ribonucleotide reduction: possible regulation mechanism.
abstract: A radical-free preparation of a highly purified ribonucleotide reductase from calf thymus was shown to generate an M2-specific tyrosine free radical on incubation with iron and dithiothreitol in the presence of air. The radical is essential for activity but once formed has a half-life of about 10 min. Using the calf thymus enzyme, there is a continual requirement of oxygen and iron for ribonucleotide reduction indicating a continual regeneration of the radical during enzyme catalysis. We therefore propose that one way a cell may regulate ribonucleotide reductase activity is by controlling the generation of M2-specific tyrosine free radicals within existing M2 molecules.
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D000818:Animals; D002417:Cattle; D004229:Dithiothreitol / Q000494:pharmacology; D005609:Free Radicals; D007501:Iron / Q000494:pharmacology*; D007700:Kinetics; D010100:Oxygen; D012264:Ribonucleotide Reductases / Q000378:metabolism*; D013950:Thymus Gland / Q000201:enzymology
chemical_list: D005609:Free Radicals; D007501:Iron; D012264:Ribonucleotide Reductases; D010100:Oxygen; D004229:Dithiothreitol