Use of feedback-resistant threonine dehydratases of Corynebacterium glutamicum to increase carbon flux towards L-isoleucine

Article Abstract:

The ilvA alleles encoding feedback-resistant threonine dehydratases increase the L-isoleucine biosynthesis in Corynebacterium glutamicum. The ilvA genes of high-copy number vectors encoding threonine dehydratase also increase the synthesis. The bacterial strain with the highest yield contains three hom(Fbr) copies encoding the feedback-resistant homoserine dehydrogenase and ilvA(Fbr) encoding feedback-resistant threonine dehydratase. High L-isoleucine formation is achieved by balancing homoserine dehydrogenase and threonine dehydratase activities with feedback-resistant aspartate kinase.

Physiological aspects, Observations, Microbial enzymes, Dehydrogenases, Oxidoreductases, Threonine, Aspartate kinase

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L-isoleucine production with Corynebacterium glutamicum: further flux increase and limitation of export

Article Abstract:

L-isoleucine commercial oversynthesis with Corynebacterium glutamicum indicates that L-isoleucine export is the limiting step for the intracellular accumulation of this amino acid. Bacterial strains are constructed using combinations of four genes and alleles encoding feedback-resistant enzymes (Fbr) to determine the effect of sequences on flux increase. The order of genes overexpressed is important, since hom(Fbr) gene can be introduced only after the overexpression of ilvA(Fbr). The intracellular L-isoleucine level is always higher than the extracellular levels in the bacterial cells.

Microbiological synthesis, Isoleucine

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D-Panthotenate synthesis in Corynebacterium glutamicum and use of panBC and genes encoding L-valine synthesis for D-panthotenate overproduction

Article Abstract:

Enzymes and genes involved in D-panthotenate synthesis by Corynebacterium glutamicum were analyzed and their use for the direct microbial synthesis of D-panthotenate was investigated. The three enzymes of the D-panthotenate synthesis quantified have specific activities of about 1 nmol/min/mg of protein, an extremely low level compared to the specific activities of enzymes of amino acid synthesis and of the central metabolism. Meanwhile, the genes panB and panC of C glutamicum appear to constitute an operon, since the sequence shows that both overlap by one nucleotide.

Chemical synthesis, Inorganic compounds, Pantothenic acid

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