The Biosynthesis of Cell Wall Lipopolysaccharide in Escherichia coli

3-Deoxy-D-manno-octulosonatealdolase, an inducible enzyme isolated from extracts of 3-deoxy-D-manno-octulosonate-grown Aerobacter cloacae, has been purified approximately 60-fold.The enzyme catalyzes the following reaction: 3-deoxy-D-manno-octulosonate -2 pyruvate + D-arabinose.Pyruvate was characterized chromatographically and with lactic acid dehydrogenase.D-Arabinose was characterized chromatographically and by its reactivity with L-fucose isomerase to form D-ribulose. The purified enzyme exhibited the following properties: pH optimum, 7; Michaelis constant = 6 X 10 -3 M; and equilibrium constant = 0.077 M. The enzyme provides a convenient method for the preparation of specifically 4 C-labeled 3-deoxy-D-manno' octulosonate.The two preceding papers in this series reported the occurrence of 3-deoxy-D-manno-octulosonate as a glycosidically bound constituent of the cell wall lipopolysaccharide of Escherichia coli 0111-B 4 and other enteric bacteria (1), and the purification and properties of cytidine monophosphate 3-deoxy-D-manno-octulosonate synthetase which catalyzes the following reaction: cytidine triphosphate + 3-deoxy-D-manno-octulosonate CMP-3-deoxy-D-manno-octulosonate + inorganic pyrophosphate (2).In a preliminary communication (3), an inducible enzyme, 3-deoxy-D-manno-octulosonate aldolase, also specifically involved in the metabolism of 3-deoxy-D-manno-octulosonate, was reported to catalyze the following reaction.