Evaluating the catalytic contribution from the oxyanion hole in ketosteroid isomerase.

ABSTRACT: Prior site-directed mutagenesis studies in bacterial ketosteroid isomerase (KSI) reported that substitution of both oxyanion hole hydrogen bond donors gives a 10(5)- to 10(8)-fold rate reduction, suggesting that the oxyanion hole may provide the major contribution to KSI catalysis. But these seemingly conservative mutations replaced the oxyanion hole hydrogen bond donors with hydrophobic side chains that could lead to suboptimal solvation of the incipient oxyanion in the mutants, thereby potentially exaggerating the apparent energetic benefit of the hydrogen bonds relative to water-mediated hydrogen bonds in solution. We determined the functional and structural consequences of substituting the oxyanion hole hydrogen bond donors and several residues surrounding the oxyanion hole with smalle

SUBMITTER: Schwans JP 

PROVIDER: S-EPMC3241876 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature