description
General Background : Chondroitin-sulfates "Chondroitin sulfate" is a sulfated : Glycosaminoglycans glycosaminoglycan" composed of alternating units of sulfated :CPD-12557 N-acetyl-beta-D-galactosamine and : CPD-12521 beta-D-glucuronate residues. The : CPD-12557 N-acetyl-beta-D-galactosamine residues are substituted to varying degrees with sulfate linked to 4- and/or 6-hydroxyl positions, forming : CPD-12516 N-acetyl-beta-D-galactosamine 4-sulfate, : CPD-12565 beta-N-acetyl-D-glucosamine 6-sulfate or : CPD-12526 N-acetyl-D-galactosamine 4,6-bissulfate, and to a lesser extent the uronic acid residues may be substituted with sulfate at the 2-hydroxyl position forming : CPD-12527 2-O-sulfo-beta-D-glucuronate. The uronic acid residues may also be substituted with sulfate at the 3-hydroxyl positions, although this substitution is quite rare. The following names have been used to define different sulfation states: : Chondroitin-Sulfate-A "Chondroitin sulfate A" contains : CPD-12521 beta-D-glucuronate and : CPD-12516 N-acetyl-beta-D-galactosamine 4-sulfate : Chondroitin-Sulfate-C "Chondroitin sulfate C" contains : CPD-12521 beta-D-glucuronate and : CPD-12565 beta-N-acetyl-D-glucosamine 6-sulfate : Chondroitin-Sulfate-D "Chondroitin sulfate D" contains : CPD-12527 2-O-sulfo-beta-D-glucuronate and : CPD-12565 beta-N-acetyl-D-glucosamine 6-sulfate : Chondroitin-Sulfate-E "Chondroitin sulfate E" contains : CPD-12521 beta-D-glucuronate and : CPD-12526 N-acetyl-D-galactosamine 4,6-bissulfate The term "chondroitin sulfate B" has been used in the past to refer to : Dermatan-Sulfate dermatan sulfate, but is not used any more. The chondroitin chains vary in size up to a hundred or more disaccharide repeating units. They are usually found attached to assorted core proteins as part of a proteoglycan complex. Chondroitin sulfate is a major component of connective tissue matrix (such as skin and cartilage), but is also found on cell surface and basement membranes and in intracellular granules of certain cells. Functions in matrix locations are mainly structural, while functions in membranes are mainly as receptors. Chondroitin sulfate chains are synthesized in situ on the protein chain. They are attached to the core protein via a specific tetrasaccharide known as the "glycoaminoglycan-protein linkage region", which is formed by sequential stepwise additions of the sugar residues to specific core proteins. The synthesis of the linkage region is described in : PWY-6557 glycoaminoglycan-protein linkage region biosynthesis, and the polymerization of the chondroitin chain is described in : PWY-6566 chondroitin and dermatan biosynthesis. About This Pathway This pathway describes the later modifications of the chondroitin chain. These modifications include the sulfation of the : CPD-12521 beta-D-glucuronate and :CPD-12557 N-acetyl-beta-D-galactosamine residues at different positions by a number of sulfotransferases with strict specificities. The sulfation of :CPD-12557 N-acetyl-beta-D-galactosamine at the 4-hydroxyl position is catalyzed by three enzymes encoded by the : HS10284 CHST11, : HS06130 CHST12 and : HS11524 CHST13 genes . The sulfation of :CPD-12557 N-acetyl-beta-D-galactosamine at the 6-hydroxyl position is catalyzed by enzymes encoded by the :HS04610 CHST3 and : HS07394 CHST7 genes . Another enzyme, encoded by : HS11694 CHST15, catalyzes the sulfation at the C6 position of residues already sulfated at the C4 position . The C2 position of : CPD-12521 beta-D-glucuronate residues is also often sulfated in a reaction catalyzed by : ENSG00000111962-MONOMER uronyl 2-sulfotransferase, encoded by the : HS03488 UST gene

external resources
NCBI:545276
BIOCYC:HUMAN_PWY-6567
PUBMED:11572857
PUBMED:10722746
PUBMED:10781601
PUBMED:10187838
PUBMED:9714738
PUBMED:10956661
PUBMED:12080076
PUBMED:9883891
PUBMED:10781596

genes
CHST2 , CHST3 , UST , CHST11 , CHST15 , CHST12 , CHST7 , CHST13 ,