The Chemistry and Biological Significance of 3-Deoxy-d-manno-2-Octulosonic Acid (KDO)

This chapter examines the chemistry and biological significance of 3-deoxy-D-manno-2-octulosonic acid (KDO). The KDO occurs as a ketosidic component in all lipopolysaccharides (LPS) of Gram-negative bacteria and it has also been identified in several acidic exopolysaccharides. The incorporation of KDO appears to be a vital step in LPS biosynthesis and in the growth of the Gram-negative bacteria. The partial protection of individual KDO residues from periodate degradation, depending on the origin of the LPS and the method of TBA analysis, suggest that a common, branched, trisaccharide structure consisting of KDO residues might actually constitute the linkage region between core oligosaccharides and lipid A in LPS from Salmonella Minnesota. It is found that when oligosaccharides containing reducing-terminal KDO residues are subjected to borohydride reduction prior to Smith degradation, the epimeric pair of oligosaccharides is obtained, containing 3-deoxy-L-ribo- and -arabino-hexonic acid at the end that had formerly been reducing. The spectroscopic analysis of KDO and of its natural derivatives is also described in the chapter.