Crystallization of β-galactosidase does not reduce the range of activity of individual molecules

By use of a capillary electrophoresis-based procedure, it is possible to measure the activity of individual molecules of beta-galactosidase. Molecules from the crystallized enzyme as well as the original enzyme preparation used to grow the crystals both displayed a range of activity of 20-fold or greater. beta-Galactosidase molecules obtained from two different crystals had indistinguishable activity distributions of 31 600 +/- 1100 and 31 800 +/- 1100 reactions min(-1) (enzyme molecule)(-1). This activity was found to be significantly different from that of the enzyme used to grow the crystals, which showed an activity distribution of 38 500 +/- 900 reactions min(-1) (enzyme molecule)(-1).