UDP-GlcNAc: Beta-gal beta1,3-NAcetylglucosaminyltransferase 6 (B3GNT6) (core 3 synthase, C3GnT)

Abstract

Mucins, which are highly glycosylated with O-linked (mucin-type) glycans, are an essential component of mucinous glycoproteins secreted from the mucosal tissue of the esophagus, stomach, and intestine. Mucin-type glycoproteins have clusters of O-glycans whose synthesis is initiated by various UDP-GalNAc: polypeptide N-acetylgalactosaminyltransferases (pp-GalNAcTs). After the addition of a GalNAc residue to a serine and/or threonine residue by pp-GalNAcT, sugar residues are sequentially transferred to GalNAc on the peptide to form O-glycans. These O-glycans can be classified into several different groups according to their core structures. As illustrated in Fig. 30.1, there are at least seven core types. Each core structure is differentially expressed in conjunction with the differentiation and malignant transformation of various cells and tissues. The expression of core 3, GlcNAcβ1-3GalNAcα-serine/threonine, is limited to mucins from specialized tissues such as colon. Core 3 O-glycan, an important precursor in the biosynthesis of mucin-type glycoproteins, is synthesized by UDP-N-acetylglucosamine: GalNAc-peptide β1,3-N acetylglucosaminyltransferase(β3GnT; core 3 synthase, C3GnT).