Many glycoproteins carry glycans initiated by GalNAc attached to the hydroxyl of Ser or Thr residues. Mucins are the class of glycoproteins carrying the greatest number of O-GalNAc glycans (also called mucin-type O-glycans), but this posttranslational modification is common among many glycoproteins. The sugars found in O-GalNAc glycans include GalNAc, Gal, GlcNAc, Fuc, and Sia, whereas Man, Glc, or Xyl residues are not represented. Sialic acids may be modified by O-acetylation, and Gal and GlcNAc by sulfation. The length of O-GalNAc glycans may vary from a single GalNAc to more than 20 sugar residues and can include blood group and other glycan epitopes. This chapter describes the structures, biosynthesis, and functions of O-GalNAc glycans in mammals.
许多糖蛋白携带由连接到丝氨酸或苏氨酸残基羟基上的N-乙酰半乳糖胺（GalNAc）起始的聚糖。粘蛋白是携带最多O-GalNAc聚糖（也称为粘蛋白型O-聚糖）的糖蛋白类别，但这种翻译后修饰在许多糖蛋白中很常见。O-GalNAc聚糖中发现的糖类包括GalNAc、半乳糖（Gal）、N-乙酰葡糖胺（GlcNAc）、岩藻糖（Fuc）和唾液酸（Sia），而甘露糖（Man）、葡萄糖（Glc）或木糖（Xyl）残基则不存在。唾液酸可能会被O-乙酰化修饰，半乳糖和N-乙酰葡糖胺会被硫酸化修饰。O-GalNAc聚糖的长度可以从单个GalNAc到超过20个糖残基不等，并且可以包括血型和其他聚糖表位。本章描述了哺乳动物中O-GalNAc聚糖的结构、生物合成和功能。
