Membrane Carbohydrate A Brief Study

MEMBRANE CARBOHYDRATE SWEET MYSTERY OF LIFE……..

Carbohydrates • Polyhydroxy aldehyde or ketone • Most abundant biomolecules on earth. • Photosynthesis fixes 100 billion ton of CO2 and H2O into Carbohydrate annually • Source of energy via Glycolysis, Krebs cycle • Insoluble carbohydrate serve as

CARBOHYDRATE

STRUCTURAL GLYCOCONJUGATE OR CARBOHYDRATE MEMBRANE CARBOHYDRATE e.g. Cellulose, Chitin STORAGE e.g. Glycolipid, Glycoprotein etc. CARBOHYDRATE etc. e.g. Starch, Glycogen etc.

MEMBRANE CARBOHYDRATE • Bound to membrane via lipid or protein • Present on both side but can vary e.g. glycolipid generally present on outer half membrane but glycoprotein on both the side. • Concentration vary with membrane to membrane • Serve as destination labels for proteins • Mediators of specific cell to cell interaction

BASED ON THE CONJUGATE

GLYCOPROTEIN

PROTEOGLYCAN

GLYCOLIPID

LIPO-POLYSACCHARIDE

GLYCOPROTEIN • Oligosaccharides of varying complexity joined to protein • Present on the outer face of plasma membrane, golgi complex, lysosome, secretory granule • Sugar portion less monotonous than glycosamine of proteoglycan • Rich in information, highly specific sites for recognition • High-affinity binding

PROTEOGLYCAN • Glycosaminoglycan covalently bound to membrane protein • Glycosaminoglycan moiety predominates the proteoglycan • Biological activity is due to glycosamine moiety

GLYCOLIPID • membrane lipids with hydrophilic end are oligosaccharide • Generally present on outer side of membrane • Oligosaccharide motif is smaller but very diverse with cell to cell. • Responsible for Human blood group type A, B, AB & O e.g. Ganglioside, Digalactosyldiglycerid e etc.

LIPOPOLYSACCHARIDE • As glycolipid are absent in bacteria(ve), it is there • Sugar motif is larger than lipid • Act as endotoxin • responsible for immune response in human

FUNCTION OF MEMBRANE CARBOHYDRATAES  Functions in cell - cell recognitionglycoprotein serve as identification tags that are specifically recognized by other cells. Mechanism through which cell recognizes other cells. cell surface contain both glycosyl transferase & their oligosaccharide substrate binding of each other’s oligosaccharide to glycosyl transferase result in adhesion,  important in cell sorting and organization in tissue and organ development 

important for recognition and rejection of foreign cells by the immune system (give a “fingerprint” -tissue rejection)

 Some adhesion between cells in the reception of signal molecules 

give rise to A, B, and O blood groups because of glycolipid present on the RBC

GLYCOPROTEIN:- Cell Receptor as point of attachment for other cells, toxin, virus, hormone and many other molecule

CONCLUSION • A great majority of proteins and many of lipids are glycosylated. Many of their structures are to be revealed and their distinct function understood. • Information embedded in oligosaccharide structure, decoded by specific receptors mediate many vital biological processes. • Impaired glycosylaton may cause diseases and be disease specific. • Surface oligosaccharides show antigenic properties and are receptor specific. • Sugar structure change during development and ageing, as well as in response to environmental factors. • Understanding glycobiology will help understanding and treating diseases.

REFERENCE:• • • •

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Robert K. Murray, Daryl K. Granner & Victor W. Rodwell: "Harper's Illustrated Biochemistry 27th Ed.", p. 526, McGraw-Hill, 2006 Biochemistry 5thE 11.3. Carbohydrates Can Be Attached to Proteins to Form Glycoproteins Molecular Biology of the Cell (3rd Edition). Alberts B, Bray D, Lewis J, Raff M, Roberts K, Watson JD. Garland Publishing Rittig MG et al (2004). "Smooth and rough lipopolysaccharide phenotypes of Brucella induce different intracellular trafficking and cytokine/chemokine release in human monocytes". Journal of Leukocyte Biology 5 (4): 196–200. PMID 12960272 Netea M et al (2002). "Does the shape of lipid A determine the interaction of LPS with Toll-like receptors?". Trends Immunol 23 (3): 135–9. doi: 10.1016/S1471-4906(01)02169-X. PMID 11864841 WWW.PUBMEDCENTRAL.GOV WWW.SCIENCEDIRECT.COM www. journalseek.net/cgibin/journalseek/journalsearch.cgi?field=issn&query=0282-0080

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