Neutral-sugar transport by rat liver lysosomes.
Transport of D-glucose was studied in Percoll-gradient-purified rat liver lysosomes. D-Glucose uptake had a Km of 22 mM and a t1/2 of approx. 30 s. D-Fucose, 2-deoxyglucose and methyl alpha-glucoside were the most effective competitors for uptake of D-glucose, although D-galactose, D-mannose, D-xylose and L-fucose also appeared to compete for uptake. L-Glucose was a poor competitor for uptake. No competition was observed with N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, D-glucuronic acid, N-acetylneuraminic acid, D-glucosamine or the amino acids L-glycine, L-lysine and L-proline. Uptake was unaffected by N-ethylmaleimide, dithiothreitol, KCl, NaCl, ATP/Mg or alteration of buffer pH. D-Glucose efflux from lysosomes was temperature-dependent, with a Q10 of 2.3, and was inhibited by cytochalasin B. Counter-transport could not be demonstrated. In contrast, L-fucose uptake had a Km of 65 mM and was largely unaffected by 5 M excess of neutral D-sugars. Both uptake and efflux of L-fucose were inhibited by cytochalasin B. It appears that lysosomes possess a facilitated transport system for D-glucose and perhaps other neutral D-sugars that is discrete from transport systems for acetylated and acidic sugars.
Jonas
A J
AJ
Division of Medical Genetics, Harbor-UCLA Medical Center, Torrance 90502.
Conrad
P
P
Jobe
H
H
D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D003571:Cytochalasin B / Q000494:pharmacology; D005260:Female; D005643:Fucose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D015636:Magnesium Chloride / Q000494:pharmacology; D009005:Monosaccharides / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000494:pharmacology; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D009005:Monosaccharides; D013439:Sulfhydryl Reagents; D015636:Magnesium Chloride; D005643:Fucose; D003571:Cytochalasin B; D012965:Sodium Chloride; D005947:Glucose