InterPro domain: IPR003560

The absence of free iron molecules in the surrounding environment triggers transcription of gene clusters that encode both siderophore-synthesis enzymes, and receptors that recognise iron-bound siderophores [ 1 ]. Classic examples are the enterobactin/enterochelin clusters found in Escherichia coli and Salmonella, although similar moieties in other pathogens have been identified. The enzymic machinery that produces vibrionectin in Vibrio cholerae is such a homologue [ 2 ].

EntA, a 2,3-dihydro-2,3-dihydroxybenzoate dehydrogenase enzyme, is the third enzyme in the biosynthesis of 2,3-dihydroxybenzoic acid (DHB) from chorismate in Escherichia coli. It converts isochorismate to DHB, used for the synthesis of iron chelator enterobactin. Bacillus subtilis possesses similar genes involved in siderophore biosynthesis [ 3 ]. Deletion studies involving EntA-mutants have shown that it is essential for virulence [ 4 ].

1. Nucleotide sequence and transcriptional organization of the Escherichia coli enterobactin biosynthesis cistrons entB and entA. J. Bacteriol. 171, 784-90
2. Cloning of a Vibrio cholerae vibriobactin gene cluster: identification of genes required for early steps in siderophore biosynthesis. J. Bacteriol. 179, 7055-62
3. Sequence and genetic organization of a Bacillus subtilis operon encoding 2,3-dihydroxybenzoate biosynthetic enzymes. Gene 178, 119-23
4. Nucleotide sequence of a cluster of Escherichia coli enterobactin biosynthesis genes: identification of entA and purification of its product 2,3-dihydro-2,3-dihydroxybenzoate dehydrogenase. J. Bacteriol. 171, 791-8