PHOSPHORYLATION OF 2-D-DEOXYGLUCOSE AND ASSOCIATED INORGANIC PHOSPHATE UPTAKE IN ASCITES TUMOR CELLS

The kinetics of 2-D-deoxyglucose and inorganic orthophosphate consumption, deoxyglucose 6- phosphate accumulation, adenine mononucleotide transformation, and respiration by Ehrlich ascites carcinomacells incubated in 2.7-5.4 mM phosphate at 23° have been measured over a 3-min period after addition of 2-o-deoxyglucose. The estimate of P:O ratios based on deoxyglucose phosphorylation varies with time, being near 3 in the first 30 sec and declining thereafter. Consistent discrepancies between deoxyglucose phosphorylation and inorganic phosphate disappearance suggests either an unidentified reservoir of “high-energy phosphate” available for adenosine triphosphate regeneration or a release of inorganic phosphate from endogenous phosphate esters during the initial periods of rapid sugar phosphorylation. The latter interpretation is favored as being consistent withLynen’s phosphate cycle concept and other known features of ascites tumor cell metabolism. In theseterms, the initial. ratio calculated from d(deoxyglucose 6-phosphate)/dt, after correction for phosphate derived from the declining adenosine triphosphate level, approaches 3 because the phosphorylation of deoxyglucose almost completely interrupts the preceding phosphorylation of endogenous substrates. As the phosphorylation of endogenous substrates increases again to compete effectively withdeoxyglucose phosphorylation, the apparent P:O ratio declines. The very low P:O ratios calculated from inorganic phosphate and oxygen uptake over a 15-min interval are shown to be invalid becauseof the sharp decline in the rate of deoxyglucose phosphorylation after 3 min. © 1969, American Chemical Society. All rights reserved.