The role of genes LAC1 and LAC2 in the biosynthesis of lactose metabolism enzymes by Kluyveromyces lactis.

By crossing different Kluyveromyces lactis strains, the role of genes LAC1, LAC2 and of gene C were analyzed. These genes are involved in the biosynthesis of enzymes for the metabolism of lactose and galactose. They control the biosynthesis of the lactose and galactose transport, of beta-galactosidase and of the three enzymes of the Leloir pathway. The presence of at least one of the LAC gene is required for the biosynthesis to occur. The gene C seems to code for a negative factor which blocks the expression of the LAC1 and LAC2 genes in the absence of an inducer.