Dec 1, 1975

3-Deoxy-D-arabino-heptulosonic acid 7-phosphate synthase mutants of Salmonella typhimurium

Journal of Bacteriology
A B DeLeo, D B Sprinson


The first committed step of aromatic amino acid biosynthesis in Salmonella typhimurium was shown to be catalyzed by three isoenzymes of 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) synthase. Mutations in each of the genes specifying the isoenzymes were isolated and mapped. aroG, the structural gene for the phenylalanine-inhibitable isoenzyme, was linked to gal, and aroH, the structural gene for the tryptophan-inhibitable isoenzyme, was linked to aroE. aroF, the structural gene for the tyrosine-inhibitable isoenzyme, was linked to pheA and tyrA, which specify the phenylalanine- and tyrosine-specific branch-point enzymes, respectively. The phenylalanine-inhibitable isoenzyme was the predominant DAHP synthase in wild-type cells, and only the tryosine-inhibitable isoenzyme was completely repressed, as well as inhibited, by low levels of its allosteric effector. The DAHP synthase isoenzymes were separated by chromatography on diethylaminoethyl-cellulose with a phosphate gradient which contained enolpyruvate phosphate to protect the otherwise unstable phenylalanine-inhibitable isoenzyme. No cross-inhibition of either the tyrosine- or phenylalanine-inhibitable isoenzyme was observed at inhibitor concentrations up to 1 mM. Th...Continue Reading

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Mentioned in this Paper

5-dehydro-3-deoxy-D-arabino-heptulosonic acid-7-phosphate
Sugar Phosphates
Enzymes, antithrombotic
2-Dehydro-3-Deoxyphosphoheptonate Aldolase
Chromatography, DEAE-Cellulose
Phosphate Measurement
Amino Acid Biosynthesis

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