The Structure of Lipid A

Lipid A is considered as the hydrophobic lipid moiety of the LPS molecule. Lipid A is basically phosphorylated glucosamine disaccharide with many fatty acids attached to it. This portion of the LPS is responsible for its endotoxic activity (Rietschel et al., 1982). Lipid A is the agent capable of inducing various endotoxic reactions such as fever, Shwartzman reaction, activation of immune cells, lethal toxicity etc (Galanos et al 1985; Rietschel et al, 1987). Lipid A is embedded in the lipid bilayer of outer membrane and is necessary for a functional membrane barrier function (Wyckoff et al., 1998). Lipid A generally consists of bisphosphorylated β-(1 6) - linked glucosamine disaccharide substituted with fatty acids ester linked at positions 3 and 3׀ and amide linked at positions 2 and 2’ (Zahringer et.al 199). Lipid A adopts an ordered hexagonal arrangement resulting in a more rigid structure compared with the rest of the molecule (Petsch and Anspach., 2000). Bacteria lacking lipid A are not known (Perola et al., 2007). LPS containing a lipid A and Kdo, a unique sugar along with ...