Glycosylation processes involve different cellular compartments.
Glycan biosynthesis and cellular compartments involved in the glycosylation process. Sugars are carried across the plasma membrane into cells or are salvaged from degraded glycoconjugates at lysosomes. Through biosynthetic and interconversion reactions, monosaccharides are activated into different nucleotide sugars. Sugar activation generally takes place in the cytoplasm, although several enzymes involved in sugar nucleotide biosynthesis in T. b. brucei are localized in the glycosome. After being activated, sugar nucleotides are transported into the endoplasmic reticulum/Golgi apparatus and used by different glycosyltransferases (GT). Glycosyltransferases and other glycan-processing enzymes define the assembly and final structure of glycans that are secreted or located in the cell surface, forming a protective glycocalyx. Sugar nucleotide transporters are marked with an asterisk (*).