- Discussion:
- two major glycosaminoglycans w/ in cartilage ground substance consist of chondroitin sulfate and keratan sulfate;
- both of these substances are covalently attached to the core protein of proteoglycan;
- their concentration and distribution w/ in matrix vary considerably according to age, type of cartilage, & morphological location within
the tissue;
- ratio of chondroitin sulfate to keratin sulfate:
- infant: 12 to 1
- adult: 2 to 1
- osteoarthritis: 10 to 1
- chondroitin sulfate:
- N-acetyl galactosamine alternates w/ glucuronic acid to form disaccharide repeating unit of polymer;
- chondroitin sulfate consists of a chain of about 40 repeating units of N-acetyl chondrosine sulfate w/ about about 80 anionic charges;
- there are about 100 chondroitin sulfate glycosaminoglycan chains per proteoglycan subunit;
- chondroitin sulfate is the most prevalent of the glycoaminoglycan in cartilage:
- concentration of chondroitin-4 sulfate steadily decreases w/ age;
- chondroitin-6 sulfate concentration increases w/ older age;
- keratan sulfate:
- disaccharide repeating unit consisting of N-acetyl glucosamine alternating w/ galactose;
- keratan sulfate has variable chain length & variable degree of sulfonation;
- present in low levels in fetal & newborn cartilage;
- concentration rises w/ maturation upto 55% of total glycosaminoglycan content of the tissue;
- of note, Morquio's Syndrome is a disorder characterized by excessive accumulation of keratin sulfate in the tissues
Synthesis of chondrocytic keratan sulphate-containing proteoglycans by human chondrosarcoma cells in long-term cell culture.