The effects of twelve monosaccharides on the oxygen uptake of Krebs-2 ascites carcinoma cells were determined during prolonged incubation. Seven sugars were shown to inhibit respiration. The incubation periods required to induce inhibition were inversely related to the maximum rate of phosphorylation of each sugar by tumor hexokinase. Of these inhibiting sugars, the nonglycolyzable were 2-deoxyglucose, glucosone, and mannoheptulose; and the glycolyzable were glucose, mannose, fructose, and glucosamine. Glucosone, a slowly phosphorylated sugar of highest affinity to hexokinase, controlled the degree of inhibition and its time of onset when added to tumor cells in combination with 2-deoxyglucose or with each of the glycolyzable hexoses. The nonphosphorylated sugars, galactose, 3-o-methylglucose, l-sorbose, lyxose, and xylose, were found to be noninhibitory to respiration.

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This work has been supported in part by Public Health Service research grant No. C-5118 from the National Cancer Institute.

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