title: Characterization of low- and high-affinity glucose transports in the yeast Kluyveromyces marxianus.
abstract: Glucose transport in the yeast Kluyveromyces marxianus proceeds by two functionally and presumably structurally distinct transporters depending on the carbon source of the culture medium. In lactose-grown cells, glucose was taken up through a high-affinity H+-sugar symporter (Km = 0.09 mM), whereas a low-affinity transporter (Km = 3.5 mM) was utilized in glucose-grown cells. The two transporters exhibited different substrate specificities. Galactose was demonstrated to be a selective substrate of the H+-glucose symporter (Km = 0.14 mM) and did not significantly enter glucose-grown cells. Fructose was a preferential substrate of the low-affinity carrier (Km = 3.5 mM), but it entered lactose-grown cells through a high-affinity H+-fructose symporter distinct from the H+-glucose one. Other putative substrates of the two glucose transporters were identified by competition experiments. 2-Deoxyglucose recognized both carriers with a similar affinity, while the non-phosphorylatable analogues 6-deoxyglucose, 3-O-methylglucose and D-fucose exhibited a 10-30 fold preference for the high-affinity transporter.
authors: Laboratory of Microbiology, Gulbenkian Institute of Science, Oeiras, Portugal.
authors: B
authors: B
authors: Gasnier
mesh_terms: D019325:3-O-Methylglucose; D001692:Biological Transport / Q000187:drug effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D003847:Deoxyglucose / Q000378:metabolism / Q000031:analogs & derivatives; D005632:Fructose / Q000378:metabolism; D005643:Fucose / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D007700:Kinetics; D007716:Kluyveromyces / Q000378:metabolism*; D008757:Methylglucosides / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D004718:Saccharomycetales / Q000378:metabolism*
chemical_list: D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D019325:3-O-Methylglucose; D005643:Fucose; D005632:Fructose; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D003847:Deoxyglucose; D005947:Glucose; C037904:6-deoxyglucose; D005690:Galactose