- See:
cartilage topics
- Discussion:
- proteoglycan is a macromolecule constructed of a protein core to which many
glycosaminoglycan chains are attached;
- to this proteoglycan aggregate,
hyaluronic acid is non covalently bound;
- in osteoarthritis, there is a characteristic reduction in a aggregrating proteoglycans;
- about 10% of wt of proteoglycan molecule is protein, and 90% is glycosaminoglycans;
- proteoglycans
carry fixed negative charges and attract a high concentration
of cations;
- negatively
chondroitin &
keratan sulfate repel each other, so that glycosaminoglycan electrostaticrepulsion along chain and between chains and
therefore chains assume a fully extended conformation;
-
sub-types:
- aggrecans (large agregating proteoglycans)
- key proteoglycan molecule in the cartilage matrix and creates the osmotic properties necessary for cartilage to resist compressive loads;
- small proteoglycans (decorin (coats the outside of the collagen fibrils), biglycan, and fibromodulin);
-
link protein:
- small glycoprotein serves to stabilize non-covalent association of the proteoglycan subunits with hyaluronic acid in aggregate;
-
protein core:
- approximately 100
chondroitin sulfate and 50
keratan sulfate chains are attached;
THE CHONDROCYTE: A CELL UNDER PRESSURE
Synthesis of chondrocytic keratan sulphate-containing proteoglycans by human chondrosarcoma cells in long-term cell culture.
Ultrastructural modifications of proteoglycans coincident with mineralization in local regions of rat growth plate.
Electron microscopic studies of cartilage proteoglycans: Direct evidence for the variable length of the chondroitin sulfate rich region of proteoglycan subunit core protein.
JA Buckwalter and LC Rosenburg. J. Biol Chem. Vol 257. 1982. p 9830-9839.
Assembly of newly synthesized proteoglycan and link protein into aggregates in cultures of chondrosarcoma chondrocytes.
JH Kimura et al. J. Biol Chemistry. Vol 255. 1980. p 7134-7143.
