= Chondroitin 4-sulfate
<Chondroitin 4-sulfate> is a positional form of <chondroitin sulfate> with sulfate substitution at the 4-position of <N-acetylgalactosamine> residues. The modification belongs to a particular position on a sugar residue within the <chondroitin> chain. It is distinct from changing the chain length or carrying out <N-sulfation of glucosamine> in a different carbohydrate framework.
<Chondroitin 4-sulfotransferase> uses <PAPS> to perform the corresponding positional transfer. The official reaction distinguishes this <enzyme> from <chondroitin 6-sulfotransferase>; a shared donor does not imply a shared attachment position.<Chondroitin 4-sulfotransferase in IUBMB Enzyme Nomenclature>[EC2.8.2.5: Reaction and Comments, 4-position and distinction from EC2.8.2.17]{ref}
An original structural comparison starts with two equal segments, each containing eight complete repeats and sixteen sugar residues. Put one sulfate group at the 4-position of each of the eight eligible amino-sugar residues in the first segment, and instead at the 6-position in the second. Both segments have eight sulfate groups, but their local arrangements differ. Counting groups establishes composition under this model, not the modified position.
This explains why a preparation's name, backbone analysis and positional characterization contribute different information. A <proteoglycan> containing a <chondroitin 4-sulfate> chain is also a larger protein–carbohydrate assembly, rather than another name for the isolated sugar chain.<Chondroitin sulfate in ChEBI>[CHEBI:37397: positional subclasses and proteoglycan has-part relation]{ref}
Back to article page
