A direct comparison of approaches for increasing carbon flow to aromatic biosynthesis inEscherichia coli
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Different approaches to increasing carbon commitment to aromatic amino acid biosynthesis were compared in isogenic strains ofEscherichia coli. In a strain having a wild-type PEP: glucose phosphotransferase (PTS) system, inactivation of the genes encoding pyruvate kinase (pykA andpykF) resulted in a 3.4-fold increase in carbon flow to aromatic biosynthesis. In a strain already having increased carbon flow to aromatics by virtue of overexpression of thetktA gene (encoding transketolase), thepykA and/orpykF mutations had no effect. A PTS glucose+ mutant showed a 1.6-fold increase in carbon flow to aromatics compared to the PTS+ control strain. In the PTS− glucose+ host background, overexpression oftktA caused a further 3.7-fold increase in carbon flow, while inactivation ofpykA andpykF caused a 5.8-fold increase. When all of the variables tested (PTS− glucose+,pykA, pykF, and overexpressedtktA) were combined in a single strain, a 19.9-fold increase in carbon commitment to aromatic biosynthesis was achieved.
Keywordsamino acids aromatics E. coli DAHP PEP
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