Role of active site residues in promoting cobalt-carbon bond homolysis in adenosylcobalamin-dependent mutases revealed through experiment and computation.

ABSTRACT: Adenosylcobalamin (AdoCbl) serves as a source of reactive free radicals that are generated by homolytic scission of the coenzyme's cobalt-carbon bond. AdoCbl-dependent enzymes accelerate AdoCbl homolysis by ∼10(12)-fold, but the mechanism by which this is accomplished remains unclear. We have combined experimental and computational approaches to gain molecular-level insight into this process for glutamate mutase. Two residues, glutamate 330 and lysine 326, form hydrogen bonds with the adenosyl group of the coenzyme. A series of mutations that impair the enzyme's ability to catalyze coenzyme homolysis and tritium exchange with the substrate by 2-4 orders of magnitude were introduced at these positions. These mutations, together with the wild-type enzyme, were also characterized in silico by

SUBMITTER: Roman-Melendez GD 

PROVIDER: S-EPMC3928028 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature