3deoxyDmannooctulosonsyra

3deoxy-D-manno-2-octulonic acid (KDO) is a sialic acid-like compound found in the outer membrane of Gram-negative bacteria. It plays a crucial role in the structural integrity and function of bacterial cell walls, particularly in species such as *Escherichia coli* and *Salmonella typhimurium*. Chemically, KDO is a nine-carbon sugar acid with a unique structure featuring a deoxy (hydrogen instead of hydroxyl) group at the third carbon and a carboxylic acid at the terminal position.

KDO is synthesized via the KDO biosynthesis pathway, which begins with the condensation of phosphoenolpyruvate (PEP) and D-mannose-8-phosphate. The enzyme KDO 8-phosphate synthase catalyzes this reaction, producing KDO 8-phosphate, which is then dephosphorylated to form free KDO. This molecule is subsequently polymerized into repeating units, often linked to lipopolysaccharides (LPS) in the bacterial outer membrane.

The presence of KDO in LPS contributes to bacterial virulence, immune evasion, and resistance to host defenses. It also serves as a target for antibiotics and vaccines, making it a key focus in antimicrobial research. Structural studies of KDO-containing polysaccharides have provided insights into bacterial pathogenesis and potential therapeutic interventions.

In addition to its biological role, KDO has been studied for its potential applications in synthetic biology and nanotechnology due to its unique chemical properties. Its synthesis and modification have been explored for the development of novel biomaterials and drug delivery systems. Overall, KDO remains an important subject in microbiology, biochemistry, and biomedical research.