Variants resistant to 2-deoxy-D-glucose have been isolated from a clonal line of pig kidney cells by serial cultivation in the presence of inhibitor. Hexokinase activity may be affected directly i n this system, since the oxidation of glucose to 6-phosphogluconate by extracts from sensitive and resistant cells is blocked by the addition of 2-deoxy-glucose to the reaction mixture. This blockage was removed by the addition of glucose-6-phosphate to the system, but not by A".
Resistant cells were found to accumulate significantly less 2-deoxyglucose-6-phosphate than sensitive cells. The rate of phosphorylation of 2-deoxyglucose, however, was higher in extracts from the resistant line. Alkaline phosphatase does not account for the reduced level of 2-deoxyglucose-6-phosphate since this enzyme is not detectable in sensitive or resistant pig kidney cells. Increased acid phosphatase activity was observed in resistant cells, but extracts with high acid phosphatase activity proved incapable of hydrolyzing either 2-deoxyglucose-%phosphate or glucose-6-phosphate. In comparative growth studies, cells resistant to 2-deoxyglucose proliferated more extensively than sensitive cells in a low glucose nutrient. They removed glucose more effectively from this medium, and were less stimulated by the addition of intermediates from the tricarboxylic acid cycle. The evidence suggests that resistance to 2-deoxyglucose in the cells under study may be based on the ability of the resistant cells to proliferate at concentrations of glucose too low to support the growth of sensitive cells.
As a competitive inhibitor of glucose metabolism, 2-deoxy-D-glucose exerts a variety of effects in carbohydrate metabolism. Nakada and Wick ('56), for example, showed that deoxyglucose retards the uptake of glucose and function in isolated preparations of rat diaphragm. Glucose, in turn, depresses the entry of 2-deoxyglucose. Within cells 2-deoxyglucose acts to repress glycolysis, and effects have been described for brain, liver slices, yeast cells, and tumors (Woodward, '52; Woodward and Hudson, '54; Laslo, Landau, Wight and Burk, '58). Studies at the enzyme level indicate that 2-deoxyglucose is phosphorylated by hexokinase in yeast (Cramer and Woodward, '52), and in brain (Sols and Crane, '54). In cultures of HeLa cells the product of this reaction, 2-deoxyglucose-6-phosphate, is not metabolized further (Barban and Schulze, '61). However, a recent report indicates that 2-deoxyglucose is incorporated into glycogen by the Novikoff ascites hepatoma (Nigam, '67). The inhibitory action of 2-deoxyglucose or its derivatives extends to a number of loci in carbohydrate metabolism. These pathways include the fructokinase, phosphohexoisomer ase , and glucose -6 -phos-