Catalyzes the isomerization of citrate to isocitrate via cis-aconitate. citrate = D-threo-isocitrate Binds 1 [4Fe-4S] cluster per subunit. Binding of a [3Fe-4S] cluster leads to an inactive enzyme. Carbohydrate metabolism; tricarboxylic acid cycle; isocitrate from oxaloacetate: step 2/2. Monomer. Forms covalent cross-links mediated by transglutaminase TGM2, between a glutamine and the epsilon-amino group of a lysine residue, forming homopolymers and heteropolymers. Belongs to the aconitase/IPM isomerase family.