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Addition of rapidly fermentable sugars to cells of the yeast Saccharomyces cerevisiae grown on non‐fermentable carbon sources causes a variety of shortterm and longterm regulatory effects, leading to an adaptation to fermentative metabolism. One important feature of this metabolic switch is the occurrence of extensive transcriptional repression of a large group of genes. We have investigated transcriptional regulation of the SUC2 gene encoding repressible invertase, and of HXKI, HXK2 and GLKI encoding the three known yeast hexose kinases during transition from derepressed to repressed growth conditions. Comparing yeast strains that express various combinations of the hexose kinase genes, we have determined the importance of each of these kinases for establishing the catabolite‐repressed state. We show that catabolite repression involves two distinct mechanisms. An initial rapid response is mediated …