Bacterial Lipopolysaccharide, OPS, and Lipid A

Synonyms

Carbohydrates; Glycoconjugates; LPS; Polysaccharide; Polysaccharide glycan

Definition

Lipopolysaccharide (LPS) is the major component of the external leaflet of the outer membrane of almost all Gram-negative bacteria. It is an amphiphilic macromolecule consisting of three structural and biosynthetically different parts: an O-specific polysaccharide (OPS) covalently linked to an oligosaccharide (core), in turn, linked to a glycolipid moiety (Lipid A). OPS is lacking in some wild-type strains. LPS is anchored by its lipid A moiety to the outer membrane and the carbohydrate part protrudes toward the exterior of the cell. OPS is usually built of a regular polysaccharide with repeating units (up to 40–50) consisting of two to eight monosaccharides. The lipid A structure consists of a β-(1 → 6)-linked 2-amino-2-deoxy-glucopyranose (GlcN) disaccharide that bears 3-(R)-hydroxy fatty acid residues, as ester linked at the 3 and 3′positions, and amide-linked at 2 and 2′ positions, which...