CMP-3-deoxy-D-manno-octulosonate (CMP-Kdo) biosynthesis is a pathway that occurs in the cytosol by which D-ribulose 5-phosphate becomes CMP-3-deoxy-D-manno-octulosonate (CMP-Kdo). Kdo is a component in the plant cell wall, specifically of pectic polysaccharide rhamnogalacturonan II. First, arabinose-5-phosphate isomerase catalyzes the conversion of D-ribulose 5-phosphate to D-arabinose 5-phosphate. Second, D-arabinose 5-phosphate is spontaneously converted into D-arabinofuranose 5-phosphate. Third, 3-deoxy-8-phosphooctulonate synthase converts D-arabinofuranose 5-phosphate into 3-deoxy-D-manno-octulosonate 8-phosphate (KDO-8P). This enzme is a homotetramer. Fourth, the predicted enzyme 3-deoxy-manno-octulosonate-8-phosphatase (coloured orange in the image) is theorized to catalyze the conversion of 3-deoxy-D-manno-octulosonate 8-phosphate (KDO-8P) into 3-deoxy-D-manno-2-octulosonate (Kdo). The last reaction is localized to the mitochondria outer membrane whereby 3-deoxy-manno-octulosonate cytidylyltransferase (coloured dark green in the image) catalyzes the conversion of 3-deoxy-D-manno-2-octulosonate (Kdo) into CMP-3-deoxy-D-manno-octulosonate (CMP-Kdo). This enzyme requires a magnesium ion as a cofactor.

CMP-3-Deoxy-D-Manno-Octulosonate (CMP-Kdo) Biosynthesis References