title: Kinetics of active alpha-glucoside transport in Saccharomyces cerevisiae.
abstract: alpha-Glucosides are the most abundant fermentable sugars in the industrial applications of Saccharomyces cerevisiae, and the active transport across the plasma membrane is the rate-limiting step for their metabolism. In this report we performed a detailed kinetic analysis of the active alpha-glucoside transport system(s) present in a wild-type strain, and in strains with defined alpha-glucoside permeases. Our results indicate that the wild-type strain harbors active transporters with high and low affinity for maltose and trehalose, and low-affinity transport systems for maltotriose and alpha-methylglucoside. The maltose permease encoded by the MAL21 gene showed a high affinity (K(m) approximately 5 mM) for maltose, and a low affinity (K(m) approximately 90 mM) for trehalose. On the other hand, the alpha-glucoside permease encoded by the AGT1 gene had a high affinity (K(m) approximately 7 mM) for trehalose, a low affinity (K(m) approximately 18 mM) for maltose and maltotriose, and a very low affinity (K(m) approximately 35 mM) for alpha-methylglucoside.
authors.affiliation: Departamento de Bioquímica, Centro do Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil. bstambuk@mbox1.ufsc.br
authors.forename: B U
authors.initials: BU
authors.lastname: Stambuk
authors.forename: P S
authors.initials: PS
authors.lastname: de Araujo
mesh_terms: D001693:Biological Transport, Active; D003470:Culture Media; D015966:Gene Expression Regulation, Fungal; D005960:Glucosides / Q000378:metabolism*; D007700:Kinetics; D008320:Maltose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008757:Methylglucosides / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D027981:Symporters / Q000235:genetics / Q000378:metabolism; D014199:Trehalose / Q000378:metabolism; D014312:Trisaccharides / Q000378:metabolism
chemical_list: D003470:Culture Media; D005960:Glucosides; D026901:Membrane Transport Proteins; D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D027981:Symporters; D014312:Trisaccharides; C067575:maltose transport system, S cerevisiae; C027020:methylglucoside; C008317:maltotriose; D008320:Maltose; C021534:maltose permease; D014199:Trehalose