Monosaccharide transport systems in the yeast Rhodotorula glutinis.
By using D-glucose, D-xylose, D-galactose and D-fructose in the strictly aerobic yeast Rhodotorula glutinis and by comparing the half-saturation constants with inhibition constants the yeast was shown to possess a single common system for D-xylose and D-galactose (Km's and Ki's all between 0.5 and 1.1 mM) but another distinct transport system for D-fructose. The transport of D-glucose has a special position in that glucose blocks apparently allotopically all the other systems observed although it uses at least one of them for its own transport. The different character of D-glucose uptake is underlined by its relative independence of pH (its "Km" is completely pH-insensitive) in contrast with all other sugars. At low concentrations, all sugars show mutual positive cooperativity in uptake, suggesting at least two transport sites plus possibly a modifier site on the carrier.
D001665:Binding Sites; D001693:Biological Transport, Active; D005632:Fructose / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D003904:Mitosporic Fungi / Q000378:metabolism*; D009005:Monosaccharides / Q000378:metabolism*; D012248:Rhodotorula / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism
D009005:Monosaccharides; D005632:Fructose; D014994:Xylose; D005947:Glucose; D005690:Galactose