Glucose transport in Crithidia luciliae.
The glucose analogue, 2-deoxy-D-glucose, was used to characterise the glucose transport system in Crithidia luciliae choanomastigotes. Uptake was temperature dependent with a Q10 of 2, and saturable with a Km of 0.22 mM and Vmax of 5.5 nmol min-1 (mg protein)-1 at 23 degrees C. Preloaded cells showed rapid exchange of intracellular 2-deoxy-D-glucose when incubated with extracellular D-glucose or 2-deoxy-D-glucose but little exchange with L-glucose. The substrate specificity of the uptake was studied using a number of D-glucose analogues. 6-Deoxy-D-glucose, 3-fluoro-3-deoxy-D-glucose and 4-fluoro-4-deoxy-D-glucose all competed for the transporter and had significant inhibitory effects on 2-deoxy-D-glucose transport. In contrast, 1-thio-beta-D-glucose, trehalose, 3-O-methyl-D-glucose, arginine, thymidine, L-sorbose and L-glucose were not inhibitory. The results imply the existence of a glucose transporter. The transport was blocked by a number of inhibitors and ionophores, including fluoride, azide, cyanide, dinitrophenol, valinomycin and nigericin. Overall, the uptake, exchange and efflux of 2-deoxy-D-glucose is consistent with transport via facilitated diffusion.
Knodler
L A
LA
School of Biochemistry, University of New South Wales, Kensington, Australia.
Schofield
P J
PJ
Edwards
M R
MR
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D003421:Crithidia / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D007893:Leishmania donovani / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D012969:Sodium Fluoride / Q000494:pharmacology; D013045:Species Specificity; D013696:Temperature; D014346:Trypanosoma brucei brucei / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology
D007476:Ionophores; D009004:Monosaccharide Transport Proteins; D014475:Uncoupling Agents; D012969:Sodium Fluoride; D003847:Deoxyglucose; D005947:Glucose