Oligosaccharides Are Synthesized by Specific Glycosyltransferases

In addition to the high specificity of glycosyltransferases, a major reason for the ordered addition in oligosaccharide synthesis is that these enzymes are found in different membrane-bound compartments. Nascent glycoproteins come in contact with particular glycosyltransferases only when they are in the cellular compartment where the glycosyltransferase is located. 

Because the biosynthesis of O- and N-linked oligosaccharides follows quite different routes, it is convenient to discuss them separately. 

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