Regulation of maltose transport and metabolism in Saccharomyces cerevisiae

Maltose metabolism in the yeast Saccharomyces cerevisiae is of great importance both for academic and industrial researchers. It requires the presence of at least one of five independent MAL loci: MAL1, MAL2, MAL3, MAL4 and MAL6. Each active locus is made of three genes: two structural genes that encode intracellular enzyme maltase and transport protein for maltose, and the third gene that encodes positive regulatory protein. Maltose is transported unchanged into the cell with the help of specific transmembrane transporter, and then it is hydrolysed by the intracellular maltase into two glucose units which are then channeled through the glycolytic pathway. The maltose metabolism in S. cerevisiae is under the control of three general regulation mechanisms: induction, glucose repression and glucose inactivation. Powerful tools of molecular biology have brought many important discoveries in transport, metabolism and regulation of the uptake of maltose in yeast cells at the molecular level. Although the knowledge on these phenomena is far from being complete, it helps us understand the sugar preference in industrial fermentations on complex substrates but also how glucose effects gene expression and entire metabolic activity in other organisms.