Directed evolution of 2-keto-3-deoxy-6-phosphogalactonate aldolase to replace 3-deoxy-D-arabino-heptulosonic acid 7-phosphate synthase

J Am Chem Soc. 2007 May 16;129(19):6130-9. doi: 10.1021/ja067330p. Epub 2007 Apr 24.

Abstract

Directed evolution of 2-keto-3-deoxy-6-phosphogalactonate (KDPGal) aldolase for microbial synthesis of shikimate pathway products provides an alternate strategy to circumvent the competition for phosphoenolpyruvate between 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) synthase and the phosphoenolpyruvate:carbohydrate phosphotransferase system in Escherichia coli. E. coli KDPGal aldolase was evolved using a combination of error-prone polymerase chain reaction, DNA shuffling, and multiple-site-directed mutagenesis to afford KDPGal aldolase variant NR8.276-2, which exhibits a 60-fold improvement in the ratio kcat/KM relative to that of wild-type E. coli KDPGal aldolase in catalyzing the addition of pyruvate to d-erythrose 4-phosphate to form DAHP. On the basis of its nucleotide sequence, NR8.276-2 contains seven amino acid changes from the wild-type E. coli KDPGal aldolase. Amplified expression of NR8.276-2 in the DAHP synthase and shikimate dehydrogenase-deficient E. coli strain NR7 under fed-batch fermentor-controlled cultivation conditions resulted in synthesis of 13 g/L 3-dehydroshikimic acid in 6.5% molar yield from glucose. Increased coexpression of the irreversible downstream enzyme 3-dehydroquinate synthase increased production of 3-dehydroshikimic acid to 19 g/L in 9.7% molar yield from glucose. Coamplification with transketolase, which increases d-erythrose 4-phosphate availability, afforded 16 g/L 3-dehydroshikimic acid in 8.5% molar yield.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 3-Deoxy-7-Phosphoheptulonate Synthase* / chemistry
  • 3-Deoxy-7-Phosphoheptulonate Synthase* / genetics
  • 3-Deoxy-7-Phosphoheptulonate Synthase* / metabolism
  • Aldehyde-Lyases* / chemistry
  • Aldehyde-Lyases* / genetics
  • Aldehyde-Lyases* / metabolism
  • Cloning, Molecular
  • Directed Molecular Evolution*
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Glucose / metabolism
  • Models, Molecular
  • Molecular Structure
  • Mutagenesis, Site-Directed
  • Phosphoenolpyruvate / metabolism
  • Plasmids
  • Recombinant Fusion Proteins* / chemistry
  • Recombinant Fusion Proteins* / genetics
  • Recombinant Fusion Proteins* / metabolism
  • Shikimic Acid / analogs & derivatives
  • Shikimic Acid / metabolism

Substances

  • Recombinant Fusion Proteins
  • 3-dehydroshikimate
  • Shikimic Acid
  • Phosphoenolpyruvate
  • 3-Deoxy-7-Phosphoheptulonate Synthase
  • Aldehyde-Lyases
  • 6-phospho-2-keto-3-deoxy-galactonate aldolase
  • Glucose