Heat map and identities of the genes that may encode enzymes involved in the Ehrlich pathway. Genes expressed at high levels are represented in red, and genes expressed at low levels are represented in black. The figure represents the transcript levels of genes in aerobic, glucose-limited chemostat cultures of S. cerevisiae CEN.PK113-7D grown with various nitrogen sources [(NH₄)₂SO₄ (NH4), asparagine (ASN), proline (PRO), phenylalanine (PHE), leucine (LEU), and methionine (MET)] (2). Transcript levels were determined with Affymetrix GeneChips YG-S98 and are the averages of results from three independent experiments.

The Ehrlich pathway. Catabolism of branched-chain amino acids (leucine, valine, and isoleucine), aromatic amino acids (phenylalanine, tyrosine, and trytophan), and the sulfur-containing amino acid (methionine) leads to the formation of fusel acids and fusel alcohols. The genes encoding the enzymes of each step are indicated.

Expression profiling of the five TPP-dependent decarboxylases genes in various mutant strains grown at a dilution rate of 0.1 h⁻¹ in carbon-limited chemostats. Expression values are the means ± standard deviations of data from at least two independent GeneChip (Affymetrix YG-S98) analyses of samples issued from different steady-state chemostat cultivations. 1, CEN.PK113-7D grown in a carbon-limited chemostat with (NH₄)₂SO₄ as the nitrogen source (64); 2, CEN.PK113-7D grown in a carbon-limited chemostat with phenylalanine as the nitrogen source (64); 3, aro10Δ strain grown in a carbon-limited chemostat with phenylalanine as the nitrogen source (64); 4, aro10Δ thi3Δ strain grown in a carbon-limited chemostat with phenylalanine as the nitrogen source (64); and 5, pdc1Δ pdc5Δ pdc6Δ aro10Δ strain grown in a carbon-limited chemostat with phenylalanine as the nitrogen source (64). Corresponding microarray data have been deposited in the Genome Omnibus Expression Database (http://www.ncbi.nlm.nih.gov/geo/) under the series accession number GSE9590 (1).