Newly induced beta-galactosidase molecules have a higher activity than thebasally expressed enzyme

Objective: The objective of this study was to compare the activities of ind ividual molecules of induced and basally expressed Escherichia coil beta-ga lactosidase, Background Data: Single-molecule assays of enzymes have determ ined that individual molecules are not identical. They differ with respect to catalytic rate. The structural cause and cellular role of this microhete rogeneity is as yet unknown. Methods: E. coli were grown and induced to pro duce beta-galactosidase by treatment with isopropyl-beta-D-thiogalactopyran oside. Cells were lysed and the beta-galactosidase assayed with capillary e lectrophoresis instrumentation utilizing post-column, laser-induced fluores cence detection. The enzyme obtained from treated cells were compared to th at from untreated cells. Results: The activity of newly induced beta-galact osidase was found to be approximately 20% greater than that of the basally expressed enzyme. This measured difference is statistically significant. Co nclusions: Production of beta-galactosidase in E. coil under differing cond itions results in differences in the activities of the individual enzyme mo lecules.