HEXOKINASE OF ESCHERICHIA COLI. ASSAY OF ENZYME ACTIVITY AND ADAPTATION TO GROWTH IN VARIOUS MEDIA.

Hexokinase was determined in extracts of Escherichia coli by measurement of the reduction of nicotinamide-adenine dinucleotide phosphate by glucose-6-phosphate dehydrogenase, and the glucose-6-phosphate formed by the action of hexokinase. This method gave reproducible results. Extracts of E. coli contained low hexokinase activity when the organism had been grown in the absence of glucose and this enzyme activity was increased after adaptation of the organism to growth on glucose. The E. coli needed 2–2·5 divisions to reach the degree of hexokinase activity of glucose-grown bacteria when transferred to salts + glucose from media not containing glucose.