lipopolysaccharide biosynthetic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways resulting in the formation of lipopolysaccharides, any of a group of related, structurally complex components of the outer membrane of Gram-negative bacteria. [GOC:ai, GOC:mr]

Lipopolysaccharide (LPS) biosynthesis is a complex and essential process in Gram-negative bacteria, encompassing the assembly of this highly immunogenic outer membrane component. It involves multiple steps, each catalyzed by specific enzymes and requiring intricate coordination. The process begins with the synthesis of lipid A, the anchor of LPS embedded in the outer membrane. Lipid A biosynthesis starts with the activation of UDP-glucose to UDP-N-acetylglucosamine (UDP-GlcNAc) by UDP-glucose pyrophosphorylase. This activated sugar is then coupled with a diglucosamine disaccharide to form the backbone of lipid A, followed by acylation with fatty acids. This process is crucial for the structural integrity and stability of the outer membrane. Next, the core oligosaccharide is synthesized, which connects lipid A to the O-antigen. The core oligosaccharide is built through sequential addition of sugars like N-acetylglucosamine, N-acetylmuramic acid, and Kdo (3-deoxy-D-manno-octulosonic acid), catalyzed by specific glycosyltransferases. The core oligosaccharide serves as a scaffold for attaching the O-antigen, which is a highly variable structure that contributes to the diversity of LPS among different bacterial species. The O-antigen is synthesized separately and subsequently linked to the core oligosaccharide via a special glycosyltransferase. The O-antigen is comprised of repeating units of sugar residues that extend outward from the cell surface. These repetitive units can be highly variable in their composition and sequence, providing antigenic diversity and contributing to the immune evasion strategies of bacteria. Finally, the completed LPS molecule is transported to the outer membrane and embedded within it. This process involves dedicated transport systems that ensure the proper orientation of the LPS molecule in the membrane. LPS biosynthesis is tightly regulated, with several genes involved in the expression of the necessary enzymes. This regulation ensures that LPS synthesis occurs only when required, avoiding excessive production that could be detrimental to the cell. In summary, lipopolysaccharide biosynthesis is a sophisticated process that encompasses several key steps: lipid A synthesis, core oligosaccharide assembly, O-antigen production, and transport to the outer membrane. This complex process is essential for the survival and pathogenesis of Gram-negative bacteria. The structural diversity of LPS contributes to the diversity of bacterial species and their ability to evade the host immune system.'
"

Proteins (1)

Compounds (2)