title: The function of adenosylcobalamin in the mechanism of ribonucleoside triphosphate reductase from Lactobacillus leichmannii.
abstract: Ribonucleoside triphosphate reductase from Lactobacillus leichmannii catalyzes the reduction of nucleotides to deoxynucleotides and uses adenosylcobalamin as a cofactor. A transient protein-based thiyl radical is essential for catalysis. Studies directed toward the elucidation of the function of adenosylcobalamin during catalysis have shown that formation of the thiyl radical and 5'-deoxyadenosine occurs in a concerted fashion with C-Co bond homolysis, that the homolysis is entropically and not enthalpically driven, that the dimethylbenzimidazole moiety of adenosylcobalamin is the axial ligand during catalysis, and that the C-Co bond is reformed after every turnover.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Lawrence
authors.forename: J
authors.initials: J
authors.lastname: Stubbe
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology; D005075:Biological Evolution; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry; D003038:Cobamides / Q000378:metabolism*; D003854:Deoxyribonucleotides / Q000096:biosynthesis; D004578:Electron Spin Resonance Spectroscopy; D019277:Entropy; D005609:Free Radicals / Q000378:metabolism; D007700:Kinetics; D007778:Lactobacillus / Q000201:enzymology*; D008024:Ligands; D016297:Mutagenesis, Site-Directed; D012264:Ribonucleotide Reductases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003038:Cobamides; D003854:Deoxyribonucleotides; D005609:Free Radicals; D008024:Ligands; D003035:Cobalt; D012264:Ribonucleotide Reductases; C000913:cobamamide