What is the structure of glycosaminoglycans?
Glycosaminoglycans chains are composed of disaccharide repeating units called disaccharide repeating regions (Table 2). The repeating units are composed of uronic acid (d-glucoronic acid or l-iduronic acid) and amino sugar (d-galactosamine or d-glucosamine).
What is the difference between glycosaminoglycans and mucopolysaccharides?
The key difference between proteoglycans and glycosaminoglycans is that proteoglycans are organic compounds containing a protein bound to a mucopolysaccharide whereas glycosaminoglycans are mucopolysaccharides containing a number of disaccharide repeating units.
What is the formation of glycosaminoglycans?
The process of GAG biosynthesis begins in the cellular cytoplasm with the synthesis of five uridine diphosphate (UDP) derived activated sugars. These sugars include UDP-glucuronic acid, UDP-N-acetylglucosamine, UDP-xylose, UDP-galactose, and UDP-N-acetylgalactosamine.
What stimulates GAG chain synthesis?
GAG biosynthesis is initiated by the formation of a GlcA-β1,3-Gal-β1,3-Gal-β1,4-Xyl tetrasaccharide primer, which is linked to serine residues of a core protein. The GAGs are built up on this linkage tetrasaccharide region by the alternate addition of N-acetylhexosamine and glucuronic acid residues (16).
What is proteoglycan and glycosaminoglycan?
Proteoglycans consist of a core protein and one or more covalently attached GAG chains (Figure 11.2). GAGs are linear polysaccharides, whose building blocks (disaccharides) consist of an amino sugar (either GlcNAc or GalNAc) and an uronic acid (GlcA and IdoA).
How are glycosaminoglycans attached to proteins?
The GAGs extend perpendicular from the core protein in a bottlebrush- like structure. The linkage of GAGs such as (heparan sulfates and chondroitin sulfates) to the protein core involves a specific trisaccharide linker : Some forms of keratan sulfates are linked to the protein core through an N-asparaginyl bond.
How do glycosaminoglycans work?
GAGs function similar to aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) by decreasing the production of harmful pro-inflammatory compounds including prostaglandins that may degrade the cartilage matrix. This results in reduced pain and inflammation, and permits cartilage synthesis to occur.
What two glycosaminoglycans account for most of the proteoglycans?
Two classes of glycosaminoglycan chains—chondroitin sulfate/dermatan sulfate and heparan sulfate/heparin—are linked to serine residues in core proteins by way of xylose (Figure 17.4).
What are glycosaminoglycans give 2 examples?
Glycosaminoglycans Structure
- Non-sulfated GAGs: For example, hyaluronic acid (HA)
- Sulphated GAGs: For example; chondroitin sulphate (CS), dermatan sulphate (DS), keratan sulphate (KS), heparin and heparin sulphate (HS).
Are glycosaminoglycans branched?
Glycosaminoglycans (formerly known as muccopolysaccharides) are disaccharides consisting of two hexose derivatives in a repeating, un-branched chain.
Why are glycosaminoglycans sulfated?
Glycosaminoglycans vary greatly in molecular mass, disaccharide construction, and sulfation. This is because GAG synthesis is not template driven like proteins or nucleic acids, but constantly altered by processing enzymes. GAGs are classified into four groups based on core disaccharide structures.
Where are glycosaminoglycans found?
All four classes of glycosaminoglycan are found in normal lungs and all except hyaluronan are bound to core proteins.