D-Glucose transport in Trypanosoma brucei. D-Glucose transport is the rate-limiting step of its metabolism

Abstract

D-Glucose and 2-deoxyglucose enter the 'long-slender' bloodstream form of Trypanosoma brucei only by means of a carrier-mediated process; no free diffusion can be observed. Permeation is not energy-dependent. The uptake is driven by the downhill concentration gradient of free substrate. The latter is maintained by the continual removal of sugar, due to the extremely high activities of the glycolytic enzymes. The permeation process is the rate-limiting step of glucose consumption, because permeation proceeds at a rate slower than metabolism. The inhibition of sugar uptake by glycerol was tested. Interactions at the carrier site can be ruled out since glucose and its 2-deoxy analog exhibit different inhibition kinetics.