2,3-Dihydroxybenzoate is synthesized from chorismate via isochorismate and 2,3-dihydroxy-2,3-dihydrobenzoate. The biosynthesis of 2,3-dihydroxybenzoate starts from chorismate being synthesized into isochorismate through isochorismate synthase entC. The N-terminal isochorismate lyase domain of EntB hydrolyzes the pyruvate group of isochorismate to produce 2,3-dihydro-2,3-dihydroxybenzoate. The conversion of this latter compound to 2,3-dihydroxybenzoate is catalyzed by the EntA dehydrogenase. This compound then interacts with L-serine and ATP through the enterobactin synthase protein complex resulting in the production of enterobactin. Enterobactin is exported into the periplasmic space through the enterobactin exporter entS. Enterobactin is then exported into the environment through the outer membrane protein TolC. In the environment, enterobactin reacts with iron to produce ferric enterobactin. It is then imported into the periplasmic space through a ferric enterobactin outer membrane transport complex. Ferric enterobactin continues it's journey and enters the cytoplasm via a ferric enterobactin ABC transporter. Once inside the cytoplasm, ferric enterobactin spontaneously releases the iron ion from the enterobactin. Alternatively, it can react with water through an enterochelin esterase resulting in the release of 2,3-dihydroxybenzoylserine, Fe3+, and hydrogen ions.

Biosynthesis of Siderophore Group Nonribosomal Peptides References