The kinetic analysis of active sucrose-H+ uptake by Saccharomyces cerevisiae revealed the presence of two transport systems with high and low affinity for sucrose. The MAL2T permease has a low affinity (K-m=120+/-20 mM) for sucrose, while the alpha-glucoside transporter encoded by the AGT1 gene is a high affinity sucrose-H+ symporter (K-m=7.9+/-0.8 mM) that increases the specific growth rate of cells growing on sucrose.