On the "Activation" of the Lactase of Escherichia coli-mutabile.

The studies reported in this paper were directed to an explanation of the puzzling phenomenon that the non-lactose-fermenting Escherichia coli-mutabile contains lactase (Deere, Dulaney and Michelson, 1939). Earlier experiments led us to believe that the antiseptics employed "activated" the lactase which was present, but inactive, in living growing cultures of the non-lactose-fermenting (white) form. Use of an antiseptic was at first necessary in determinations of lactase activity since it protected the digest against contaminants and rendered the preparations incapable of attacking glucose and galactose. It was later found that lactase activity of preparations of the white form did not depend on the presence of, or preliminary treatment with, an antiseptic. Drying of cell suspensions by vacuum distillation suffices to "activate" the lactase. We have investigated more extensively the effect of drying on the various enzyme activities of these organisms. The drying process, unlike the various lactase "activating" antiseptics which we have employed, only partially inhibits the enzyme system or systems concerned in the metabolism of glucose and galactose. Hence, reduction methods for sugars present great difficulties in evaluating results obtained on digests in which the reducing value is being increased by one process (lactose hydrolysis) and