Kinetics of active α‐glucoside transport in Saccharomyces cerevisiae

α‐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 α‐glucoside transport system(s) present in a wild‐type strain, and in strains with defined α‐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 α‐methylglucoside. The maltose permease encoded by the MAL21 gene showed a high affinity ( K m ∼5 mM) for maltose, and a low affinity ( K m ∼90 mM) for trehalose. On the other hand, the α‐glucoside permease encoded by the AGT1 gene had a high affinity ( K m ∼7 mM) for trehalose, a low affinity ( K m ∼18 mM) for maltose and maltotriose, and a very low affinity ( K m ∼35 mM) for α‐methylglucoside.