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Biochemistry

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Synthesis and Degradation of Glycosphingolipids

BIOCHM-BLLMLJ

Glycosphingolipids, along with glycosaminoglycans and similar glycoproteins, are fairly complex biomolecules synthesized in multiple steps. Multiple enzymes, often glycosyl transferases specific for each sugar and acceptor, are involved. The mature molecule is often modified, particularly with the addition of sulfate groups attached by specific sulfotransferases. When it comes to degradation, glycosphingolipids and glycosaminoglycans are endocytosed into lysosomes. Once there, lysosomal enzymes cleave specific bonds until the molecules are fully degraded.

What general pattern holds TRUE for degradation of glycosphingolipids?

A

Components are removed in the same order they were attached, that is, "first on, first off."

B

Components are removed in the reverse order they were attached, that is, "last on, first off."

C

Components are removed in random order; whichever lysosomal enzyme binds first will perform its cleavage reaction first.

D

Components are all removed nearly simultaneously, with multiple lysozymes binding and acting at the same time. This can occur in two or three steps for particularly complex glycosphingolipids.