Ceramide, composed of a fatty acid and a sphingoid base linked by an N-acyl linkage, is the common lipid moiety of glycosphingoslipids (GSLs). Ceramide is synthesized in the ER, from where it is transported to the Golgi apparatus, and glycosylated in a stepby- step manner by various glycosyltransferases. After recycling from plasma membranes and intracellular organella, GSLs are finally sorted into the lysosomes where they are degraded by various exoglycosidases and ceramidase with the aid of corresponding activator proteins. Ceramidase is an enzyme capable of hydrolyzing the N-acyl linkage between a fatty acid and a sphingoid base in a free ceramide. Cermaidase can be classi- fied into three groups (acid, neutral, and alkaline enzymes) depending on their pH optima. It is worth noting that the three types of ceramidase are completely different in primary structure, suggesting that the isotypes of the enzyme are derived from different ancestral genes. This section deals with ceramidases and related enzymes. The action modes of enzymes described in this section are shown in Fig. 1.
KeywordsSodium Cholate Sphingoid Base Alkaline Enzyme Acid Ceramidases Choline Phosphate
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