Biosynthesis Golgi apparatus

Mucins are a class of O-linked glycoproteins that are distributed on the surfaces of epithelial cells of the respiratory, gastrointestinal, and reproductive tracts. The Golgi apparatus plays a major role in glycosyla-tion reactions involved in the biosynthesis of glycoproteins. 

The synthesis of the core proteins occurs in the endoplasmic reticulum, and formation of at least some of the above linkages also occurs there. Most of the later steps in the biosynthesis of GAG chains and their subsequent modifications occur in the Golgi apparatus. 

Key Words Plant cell-wall Pectin biosynthesis Methylester Golgi apparatus. 

Brown, R. M., Herth, W., Franke, W. W., Romanovicz, D. The role of the Golgi apparatus in the biosynthesis and secretion of a cellulosic glycoprotein in Pleurochrysis a model system for the synthesis of structural polysaccharides. In Biogenesis of plant cell wall polysaccharides, pp. 207. Loewus, F. (ed.). New York Academic Press 1973... 

The biosynthesis of O-Iinked oligosaccharides follows a different scheme. In contrast with the dolichyl pyrophosphate-mediated synthesis of N-linked oligosaccharides, the glycosyltransferases necessary for the synthesis of O-linked oligosaccharides are located in the Golgi apparatus [9]. Monosaccharide residues are added sequentially to the growing oligosaccharide chain. 

In addition to their plasma membrane eukaryotic cells also contain internal membranes that define a variety of organelles (fig. 17.2). Each of these organelles is specialized for particular functions The nucleus synthesizes nucleic acids, mitochondria oxidize carbohydrates and lipids and make ATP, chloroplasts carry out photosynthesis, the endoplasmic reticulum and the Golgi apparatus synthesize and secrete proteins, and lysosomes digest proteins. Additional membranes divide mitochondria and chloroplasts into even finer, more specialized subcompartments. Like the plasma membrane, organellar membranes act as barriers to the leakage of proteins, metabolites, and ions they contain transport systems for import and export of materials, and they are the sites of enzymatic activities as diverse as cholesterol biosynthesis and oxidative phosphorylation. 

The final reactions for the biosynthesis of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol all occur on the cytosolic surface of the endoplasmic reticulum and Golgi apparatus (fig. 19.9). By contrast, phosphatidylglycerol and diphosphatidylglycerol are synthesized on the mitochondrial membrane where they remain for the most part. 

Glycoproteins are synthesized by passing through two organelles, the ER and the Golgi apparatus [4], The biosynthesis of N-linked oligosaccharides initiates with the cytosolic transfer of GlcNAc from its uridine diphosphate (UDP) form onto dolichol... 

The biosynthesis of oligomers and polysaccharides at the plasma membrane and ER-Golgi apparatus (i.e., polysaccharide synthases and glycosyl transferases)... 

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