<p>Iron is essential for growth in both bacteria and mammals. Controlling theamount of free iron in solution is often used as a tactic by hosts to limitinvasion of pathogenic microbes; binding iron tightly within proteinmolecules can accomplish this. Such iron-protein complexes include haem inblood, lactoferrin in tears/saliva and transferrin in blood plasma. Somebacteria express surface receptors to capture eukaryotic iron-bindingcompounds, while others have evolved siderophores to scavenge iron fromiron-binding host proteins [<cite idref="PUB00006650"/>].</p><p>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 [<cite idref="PUB00006626"/>]. Classicexamples are the enterobactin/enterochelin clusters found in Escherichiacoli and Salmonella spp., although similar moieties in other pathogens have been identified. The enzymic machinery that produces vibrionectin in Vibriocholera is such a homologue [<cite idref="PUB00006668"/>].</p><p>EntB, an isochorismate enzyme, is involved in the second stage of enterobactin biosynthesis. It has a molecular weight of 35kDa, and is believed to possess bifunctional activity. Deletion studies involving EntB- mutants have shown that it is essential for virulence [<cite idref="PUB00006627"/>].</p><p>This group represents an isochorismatase.</p> Isochorismatase