Dwight B. McNair Scott

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.

Nitrobenzimidazoles as inducers of glucose 6-phosphate dehydrogenase in Escherichia coli

Abstract Extracts of cultures of Escherichia coli B grown in the presence of nitrobenzimidazoles contain increased activity of glucose 6-phosphate dehydrogenase. The ratio of activity of glucose 6-phosphate dehydrogenase to the activity of 6-phosphogluconate dehydrogenase may be as high as 8, whereas the ratio for cultures not exposed to drugs is between 1 and 2. The magnitude and kind of effect of the drug depend on the position of the nitro group on the ring with position 4 more effective than 6. Another substituent on the 6-position modifies the effect of the 4-NO 2 so that the 4-NO 2 ,6-NH 2 benzimidazole was most effective in decreasing cell division without much effect on other parameters of growth, while the 4-NO 2 ,6-Cl benzimidazole was more toxic and also the most effective inducer of synthesis of glucose 6-phosphate dehydrogenase.