Multiple enzyme regulation in the metabolic control of the leucine biosynthetic pathway at the protein level. In vivo relative changes in enzyme levels from μ = 0.1 to 0.2/h, under carbon- (C) and phosphate- (P) limiting conditions are indicated by the lengths of the gray and white bars next to each enzyme. Their position under or above the baseline indicates downregulation or upregulation, respectively. Leucine biosynthesis diagram and nomenclature from ; diagram drawn with Cell Designer  and Adobe Illustrator . Enzymes consistently upregulated under both conditions are marked in red. Metabolic steps (enzymes): Ilv2p, acetolactate synthase; Ilv6p, regulatory subunit of acetolactate synthase; Ilv5p, acetohydroxyacid reductoisomerase; Ilv3p, dihydroxyacid dehydratase; Leu4p, 2-isopropylmalate synthase (main isozyme); Leu9p, 2-isopropylmalate synthase (minor isozyme); Leu1p, isopropylmalate isomerase; Leu2p, 3-isopropylmalate dehydrogenase; Bat1p, mitochondrial branched-chain aminoacid aminotransferase; Bat2p, cytosolic branched-chain amino-acid aminotransferase.