In Vitro Kinetic Analysis of Substrate Specificity in Enterobactin Biosynthetic Lower Pathway Enzymes Provides Insight into the Biochemical Function of the Hot Dog-Fold Thioesterase EntH

The Escherichia coli siderophore enterobactin is assembled from 2,3-dihydroxybenzoate (2,3-DHB) and l-serine by the nonribosomal peptide synthetases EntB and EntF. The processive thiol-template strategy used can be sabotaged by EntB misacylation. Through in vitro kinetic analysis, we demonstrate two potential routes to EntB misacylation and provide evidence for two mechanisms by which the hot dog-fold thioesterase EntH can potentially prevent or reverse EntB misacylation.