Carbon catabolite repression: not only for glucose.

Most organisms prefer to utilize glucose as a carbon source. Accordingly, the expression of genes involved in the catabolism of other carbon sources is repressed by the presence of glucose in a process known as (carbon) catabolite repression. However, much less is known about the relationships between "poor" carbon sources. We have recently shown that the enzyme alcohol dehydrogenase of the yeast Saccharomyces cerevisiae (ADH2), required for the utilization of ethanol, is not only inhibited by glucose, but by the acetate imported from the medium or produced by ethanol metabolism. Our study showed that sensing of acetate takes place within the cell, and not in the external medium, and that "poor" carbon sources are also utilized according to a pre-established hierarchy.