Derepression of certain aromatic amino acid biosynthetic enzymes of Escherichia coli K 12 by growth in Fe3+ deficient medium

Abstract

3 Deoxy arabino heptulosonic acid 7 phosphate synthase, prephenate dehydratase, tryptophan synthase, and 2,3 dihydroxybenzoylserine synthase enzyme activities are derepressed in wild type E. coli K 12 cells grown on Fe3+ deficient medium. This derepression is reversed when FeSO4 is added to the growth medium. Addition of shikimic acid to the Fe3+ deficient growth medium causes repression of the first three enzyme activities but not of 2,3 dihydroxybenzoylserine synthase activity. Addition of 2,3 dihydroxybenzoic acid to the Fe3+ deficient growth medium has no effect on any of the above mentioned enzyme activities. The Fe3+ deficiency mediated derepression of 3 deoxy arabino heptulosonic acid 7 phosphate synthase activity is due to an elevation of the tyrosine sensitive isoenzyme; the phenylalanine sensitive isoenzyme is not derepressed under these conditions.