ABSTRACT
Single molecule assays were performed on the enzyme E. coli ß-glucuronidase using a capillary electrophoresis-based protocol. Electrophoretic mobility, catalytic rate and activation energy of catalysis were all found to be heterogeneous. The average mobility at 22°C was -1.1×10-8±0.1m2V-1s-1 (N=49) with a total range of -0.6 to -1.3×10-8m2V-1s-1. The range in electrophoretic mobility suggests that the differences in shape or charge of the individual molecules underlying the heterogeneity are likely minimal. The average catalytic rate at 22°C was 37,000±19,000min-1 (N=49) with a total range of 14,000 to 130,000min-1. Both of these properties were measured simultaneously for each of the molecules. There was a weak correlation (r2=0.43) between mobility and rate with the molecules with a less negative mobility having a tendency to have a higher rate. The average activation energy of catalysis, as determined by comparing rates at 22 and 35°C, was found to be 48±18kJmol-1 (N=7) with a total range of 18-66kJmol-1.
