Requires Mg2+. The enzyme is involved in the biosynthesis of aerobactin, a dihydroxamate siderophore. It belongs to a class of siderophore synthases known as type A nonribosomal peptide synthase-independent synthases (NIS). Type A enzymes are responsible for the formation of amide or ester bonds between polyamines or amino alcohols and a prochiral carboxyl group of citrate. The enzyme is believed to form an adenylate intermediate prior to ligation.