Simulation of Metabolic Flux from Aspartate to the Branched Chain Amino Acid (BCAA) Biosynthetic Pathways in E. coli K12. A. The metabolic network from glucose, through TCA cycle, to amino acids. The mathematical model of colored pathways was simulated here. Each color represents an operon that regulates the same color enzyme levels in the network. B. The abbreviations of enzymes: TDA, threonine deaminase; AHAS, acetohydroxy acid synthase; IR, acetohydroxy acid isomeroreductase; DAD, dihydroxy acid dehydrase; TB, transaminase B; TC, transaminase C; IPMS, α-isopropylmalate synthase; IPMI, α-isopropylmalate isomerase; IPMDH, β-isopropylmalate dehydrogenase; LIV-I, leucine, isoleucine, and valine transporter I; LS, leucine specific transporter, AKI, aspartate kinase I; AKIII, aspartate kinase III; HDHI, homoserine dehydrogenase I; ASD, semialdehyde dehydrogenase; HSK, homoserine kinase; TS, threonine synthase. The abbreviations of metabolites: Thr, threonine; Ile, isoleucine; Val, valine; Leu, leucine; Glu, glutamate; Ala, alanine; Pyr, pyruvate; αKB, α-ketobutyrate; αAL, α-acetolactate; αAHB, α-aceto-hydroxybutyrate; αDHIV, α,β-dihydroxy-isovalerate; αDMV, α, β-dihydroxy-β-methylvalerate; αKIV, α-ketoisovalerate; αKMV, α-keto-β-methylvalerate; αKG, α-ketoglutarate; αIPM, α-isopropylmalate; βIPM, β-isopropylmalate; αKIC, α-ketoisocaproate; ex-Ile, extracellular isoleucine; ex-Val, extracellular valine; ex-Leu, extracellular leucine, Asp, aspartate; AspP, Aspartyl phosphate; ASA, aspartate semialdehyde; Hse, homoserine; HseP, homoserine phosphate. kMech models used for each enzyme are italicized. Allo: allosteric, Sim: simple, PBiBi: Ping Pong Bi Bi enzyme mechanisms. Enzyme reactions are indicated by arrows. Feedback inhibition patterns are indicated by dashed lines. Activation is indicated by a plus sign, and inhibitions are indicated by vertical bars.