Biosynthesis of aromatic compounds: 13C NMR spectroscopy of whole Escherichia coli cells.

Abstract

13C and 31P NMR spectra of wild-type E. coli showed resonances from metabolic intermediates of glycolysis and ATP formation, but no detectable signals from aromatic amino acids. Tyrosine biosynthesis from D-[1-13C]glucose was observed in cells harboring a feedback-resistant allele of aroF, the gene encoding tyrosine-sensitive 3-deoxy-D-ara-bino-heptulosonate-7-phosphate synthase [7-phospho-2-keto-3-deoxy-D-arabino-heptonate D-erythrose-4-phosphate-lyase (pyruvate-phosphorylating), EC 4.1.2.15], one of the isoenzymes that control C flow through the common aromatic biosynthetic pathway. A similar accumulation of tyrosine and phenylalanine is seen in cells carrying a multiple-copy plasmid that carries a wild-type aroF allele in addition to pheA and tyrA, the structural genes for controlling enzymes of the terminal pathways to phenylalanine and tyrosine biosynthesis. These in vivo measurements by a noninvasive probe suggest feedback inhibition as the quantitatively major mechanism controlling C flow in the common aromatic compound biosynthetic pathway. In strains accumulating aromatic amino acids, a transient accumulation of trehalose was detected, indicating that previously unknown changes in E. coli metabolism accompany overproduction of aromatic compounds.