Required for optimal enterobactin synthesis. Acts as a proofreading enzyme that prevents EntB misacylation by hydrolyzing the thioester bound existing between EntB and wrongly charged molecules (By similarity). Siderophore biosynthesis; enterobactin biosynthesis. Homotetramer. Dimer of dimers. Interacts specifically with the aryl carrier protein (ArCP) domain of EntB. Belongs to the thioesterase PaaI family.