What is "oligosaccharyltransferase"

n. (context enzyme English) Any enzyme that catalyzes the transfer of an oligosaccharide

Oligosaccharyltransferase or OST is a membrane protein complex that transfers a 14- sugar oligosaccharide from dolichol to nascent protein. It is a type of glycosyltransferase. The sugar GlcManGlcNAc (where Glc= Glucose, Man= Mannose, and GlcNAc= N-acetylglucosamine) is attached to an asparagine (Asn) residue in the sequence Asn-X- Ser or Asn-X- Thr where X is any amino acid except proline. This sequence is called a glycosylation sequon. The reaction catalyzed by OST is the central step in the N-linked glycosylation pathway.