= Biochemical sulfation
\b[Biochemical sulfation] is an <enzyme>-catalyzed transfer of a sulfo group to a biological acceptor. In many such reactions, <PAPS> supplies the group and becomes <adenosine 3',5'-bisphosphate>. A <sulfotransferase> determines which acceptor and attachment site participate; a supply of free <sulfate> alone does not specify that chemical change.<Enzyme Nomenclature by the IUBMB>[EC 2.8.2.8 and EC 2.8.2.17, accepted reactions and PAPS glossary.]{ref}
Two examples distinguish the atom receiving the group. <Heparan sulfate glucosamine N-sulfotransferase> modifies a <glucosamine> nitrogen within <heparan sulfate>. <Chondroitin 6-sulfotransferase> instead modifies the 6-position oxygen of <N-acetylgalactosamine> residues in <chondroitin>. The latter activity differs from that of <chondroitin 4-sulfotransferase>, even though the donor and broad class of acceptor are similar.<Chondroitin 6-sulfotransferase in IUBMB Enzyme Nomenclature>[EC 2.8.2.17, Reaction and Comments: 6-position modification and distinction from EC 2.8.2.5.]{ref}
For an illuminating structural comparison, imagine two otherwise identical chains modified at different sugar positions. Counting sulfur atoms could give the same total for both, while their <chemical structures> differ. Identifying <biochemical sulfation> therefore requires both the group-transfer reaction and its location, rather than merely an increase in total sulfur.
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