Escherichia coli β-galactosidase is heterogeneous with respect to the activity of individual molecules

Escherichia coli β-galactosidase molecules were incubated with fluorogenic substrate in a capillary. Upon flushing the reactor contents past the detector, individual randomly distributed peaks of product were observed, each representing the activity of an individual enzyme molecule. Individual molecules were found to differ with respect to their activities. Molecules showed a 23-fold distribution of activities with the majority of molecules within a 4-fold distribution.