title: Construction of L-lysine-, L-threonine-, and L-isoleucine-overproducing strains of Corynebacterium glutamicum.
abstract: The gram-negative bacterium Corynebacterium glutamicum is used for the industrial production of amino acids, for example, of L-glutamate and L-lysine. By cloning and expressing the various genes of the L-lysine pathway in C. glutamicum, we would demonstrate that an increase of the flux of L-aspartate semialdehyde to L-lysine could be obtained in strains with increased dihydrodipicolinate synthase activity. Recently we detected that in C. glutamicum two pathways exist for synthesis of D,L-diaminopimelate and L-lysine. Mutants defective in one pathway are still able to synthesize enough L-lysine for growth, but the L-lysine secretion is reduced to 50 to 70%. Using NMR spectroscopy, we could calculate how much of the L-lysine secreted into the medium is synthesized via either one or the other pathway. Amplification of the feedback inhibition insensitive homoserine dehydrogenase and homoserine kinase in a high L-lysine-overproducing strain enabled channeling of the carbon flow from the intermediate aspartate semialdehyde towards homoserine, resulting in a high accumulation of L-threonine. For a further flux from L-threonine to L-isoleucine, the allosteric control of threonine dehydratase was eliminated.
authors.affiliation: Institut für Biotechnologie Forschungszentrum Jülich GmbH, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Sahm
authors.forename: L
authors.initials: L
authors.lastname: Eggeling
authors.forename: B
authors.initials: B
authors.lastname: Eikmanns
authors.forename: R
authors.initials: R
authors.lastname: Krämer
mesh_terms: D001709:Biotechnology / Q000379:methods; D003352:Corynebacterium / Q000235:genetics / Q000378:metabolism*; D003960:Diaminopimelic Acid / Q000378:metabolism; D005798:Genes, Bacterial; D006715:Homoserine Dehydrogenase / Q000378:metabolism; D006836:Hydro-Lyases / Q000096:biosynthesis; D007532:Isoleucine / Q000096:biosynthesis*; D008239:Lysine / Q000096:biosynthesis*; D016296:Mutagenesis; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D017433:Protein Structure, Secondary; D013912:Threonine / Q000096:biosynthesis*; D013913:Threonine Dehydratase / Q000737:chemistry / Q000378:metabolism
chemical_list: D007532:Isoleucine; D013912:Threonine; D003960:Diaminopimelic Acid; D006715:Homoserine Dehydrogenase; D017853:Phosphotransferases (Alcohol Group Acceptor); C021370:homoserine kinase; D006836:Hydro-Lyases; D013913:Threonine Dehydratase; C020040:4-hydroxy-tetrahydrodipicolinate synthase; D008239:Lysine