Kärnoligosackarider

Kärnoligosackarider are short chains of monosaccharides that constitute the core region of certain glycoconjugates. The term derives from Swedish, where “kär” means core and “oligosackarider” refers to oligosaccharides. In the context of bacterial lipopolysaccharides (LPS), the core oligosaccharide links the lipid A moiety to the outer O‑antigen polysaccharide and varies between species in both length and composition.

Typical core oligosaccharides consist of 5 to 12 sugar residues, including hexoses such as glucose or galactose, hexuronic acids, and occasionally non‑hexose residues such as heptoses or 3‑deoxy‑manno‑2‑octulosonic acid (Kdo). The composition is usually asymmetric, with an inner core closer to lipid A and an outer core that may contain additional sugars or modifications, including phosphates or acetamido groups. Variations in core structure can influence membrane stability, permeability, and the ability of bacteria to evade host immune responses.

Enzymatic assembly of the core oligosaccharide involves a series of glycosyltransferases located in the periplasmic space or membrane. Each enzyme transfers a specific sugar from a nucleotide‑activated donor to the growing chain, with the final steps often catalyzed by a Kdo transferase. Mutations that affect core oligosaccharide synthesis can lead to altered LPS structure and impact bacterial fitness.

Core oligosaccharides are of interest in vaccine design and diagnostic assays because their structure is relatively conserved within species but distinct across species. Antibodies that recognize core-specific epitopes can provide cross‑reactive protection or serve as markers for bacterial identification. In addition, synthetic analogues of core oligosaccharides are used as standards in mass spectrometry and chromatography to accurately assess LPS composition.

The study of kärnoligosackarider is therefore integral to microbiological research, vaccine development, and biotechnology, providing insights into bacterial outer membrane architecture and host‑pathogen interactions.