Abstract
A new pattern of control by feedback inhibition has been observed in the multi-branched pathway of aromatic acid biosynthesis in Bacillus subtilis . In vitro and in vivo experiments show that DAHP† synthetase, the first enzyme of the pathway, is feedback inhibited by two intermediary metabolites of the pathway, prephenic acid and chorismic acid. The inhibition is non-competitive with respect to both substrates. These metabolites are the last of the sequence of intermediates which is common to the synthesis of the end-products of the pathway. Prephenate and chorismate inhibit 50% of DAHP synthetase activity at concentrations of 5×10 −5 M and 4×10 −4 M , respectively. Except for the latter quantitative difference, chorismic and prephenic acids appear to be qualitatively identical inhibitors of DAHP synthetase. The relationships of prephenic and chorismic acids to DAHP synthetase and to the amino acid end-products are discussed in the context of the physiological significance of this unusual pattern of metabolic control.
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