Enterobactin chorismate

Figure 4. Biosynthetic pathway from chorismate to enterobactin showing nature of the class I and class II mutations in Salmonella typhimurium LT-2...

The exbB mutants (47) are derepressed in enterobactin synthesis and produce this siderophore in iron-containing media. The means whereby iron represses enterobactin synthesis is still obscure. Several years ago it was noted that growth of E. coli on low iron media led to changes in various fRNAs (77). In E. coli K-12 aromatic amino-acid synthesizing enzymes are also derepressed in low iron media, possibly because of the diversion of the chorismate pool to enterobactin (78). 

Walsh CT, Liu J, Rusnak F, Sakaitani M. Molecular studies on enzymes in chorismate metabolism and the enterobactin biosynthesis pathway. Chem. Rev. 1990 90 1105-1129. 

At the branching point of chorismic acid, either anthranilic acid, the precursor of tryptophan, or prephenic acid, the precursor of phenylalanine, itself the precursor of tyrosine and dopa (3,4-dihydroxy-phenylalanine), is formed (Fig. 10). Phosphorylation at the 3-position, condensation with phosphoenolpyru-vate, and elimination of phosphoric acid yields choris-mate from shikimate. Chorismate is also the precursor of a number of simple, and very important, aromatic compounds, including salicylic acid, 4-amino-benzoic acid (PABA), a constituent of folic acid, and 2,3-dihydroxybenzoic acid, a key acylating group of enterobactin. 

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