Biosynthesis of lipid A. Enzymatic incorporation of 3-deoxy-D-mannooctulosonate into a precursor of lipid A in Salmonella typhimurium.

The cell envelope fraction of Salmonella typhimurium contains an enzyme system which catalyzes transfer of 3-deoxyoctulosonate (KDO) from CMP-KDO to an incomplete, KDO-deficient precursor of lipid A. The enzyme system is firmly membrane-bound, but has been solubilized by treatment with nonionic detergent at alkaline pH and partially purified. Both the particulate and partially purified fractions catalyzed formation of a single reaction product containing 2 residues of KDO. Periodate oxidation of the purified product permitted tentative identification of the KDO disaccharide structure as KDO2-4KDO.