Involved in the biosynthesis of the catechol siderophore vulnibactin. Vulnibactin is a chelating compound involved in transporting iron from the bacterial environment into the cell cytoplasm. H2O + isochorismate = (2S,3S)-2,3-dihydroxy-2,3-dihydrobenzoate + pyruvate Binds 1 phosphopantetheine covalently. Siderophore biosynthesis; vulnibactin biosynthesis. Belongs to the isochorismatase family.