(KDO)3-lipid IVA (2-4) 3-deoxy-D-manno-octulosonic acid transferase (, KDO transferase, waaA (gene), kdtA (gene), 3-deoxy-D-manno-oct-2-ulosonic acid transferase, 3-deoxy-manno-octulosonic acid transferase) is an enzyme with systematic name CMP-3-deoxy-D-manno-oct-2-ulosonate:(KDO)3-lipid IVA 3-deoxy-D-manno-oct-2-ulosonate transferase ((2->4) glycosidic bond-forming). This enzyme catalyses the following chemical reaction
The enzyme from Chlamydia psittaci transfers four KDO residues to lipid A, forming a branched tetrasaccharide.