Kinetic analysis of 2-deoxy-D-glucose uptake in Saccharomyces fragilis

During uptake of 2-deoxy-D-glucose by Saccharomyces fragilis an alkalinization of the medium occurs, suggesting the possibility that deoxyglucose may be a substrate of a proton symport system. Therefore the uptake kinetics were analyzed according to the criteria presented in a previous paper. It is shown that transport proceeds via only one uptake system. Both the kinetic parameters and the steady-state accumulation level appeared to be virtually pH-independent. Deoxyglucose uptake stimulates H+-influx and K+-efflux. However, the H+/deoxyglucose stoichiometry appeared to depend on pH. It is discussed that deoxyglucose uptake can not be interpreted in terms of proton symport, but that the experimental data are in accordance with the previously proposed phosphotransferase transport system.