Mechanism of transport-associated phosphorylation of 2-deoxy-D-glucose in the yeast Kluyveromyces marxianus: characterization of the phosphoryl source

Abstract The mechanism of 2-deoxy- d -glucose transport via the glucose/fructose carrier in Kluyveromyces marxianus has been studied by comparing the concentrations and specific activities of polyphosphate, orthophosphate, ATP and sugar phosphate in cells, pulse-labeled with [ 32 P]orthophosphate. During aerobic 2-deoxyglucose uptake, phosphate accumulates in the sugar phosphate pool, whereas both the orthophosphate- and the polyphosphate pool diminish. Comparison of the specific activities suggests that ATP is the primary phosphoryl donor. ATP is recycled at the expense of orthophosphate. Polyphosphate appears to replenish the orthophosphate pool and therefore has, at least mainly, an indirect role in sugar phosphorylation. Reduction of the ATP concentration results in a decrease of the 2-deoxyglucose transport rate. The uptake velocity can be increased again by raising the ATP level. These results corroborate the conclusion that ATP donates the phosphoryl group to the sugar.