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تسجيل

Biosynthesis of Triacylglycerols:- Sphingolipid and Glycerophospholipid Synthesis Share Precursors and Some Mechanisms

المؤلف:  David L. Nelson، Michael M. Cox

المصدر:  Lehninger Principles of Biochemistry

الجزء والصفحة:  p814 -815

2026-07-01

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Biosynthesis of Triacylglycerols:- Sphingolipid and Glycerophospholipid Synthesis Share Precursors and Some Mechanisms

The biosynthesis of sphingolipids takes place in four stages: (1) synthesis of the 18-carbon amine sphinganine from palmitoyl-CoA and serine; (2) attachment of a fatty acid in amide linkage to yield N-acylsphinga nine; (3) desaturation of the sphinganine moiety to form N-acylsphingosine (ceramide); and (4) attach ment of a head group to produce a sphingolipid such as a cerebroside or sphingomyelin (Fig. 21–31). The pathway shares several features with the pathways leading to glycerophospholipids: NADPH provides re ducing power, and fatty acids enter as their activated CoA derivatives. In cerebroside formation, sugars enter as their activated nucleotide derivatives. Head-group attachment in sphingolipid synthesis has several novel aspects. Phosphatidylcholine, rather than CDP-choline, serves as the donor of phosphocholine in the synthesis of sphingomyelin. In glycolipids, the cerebrosides and gangliosides (see Fig. 10–12), the head-group sugar is attached directly to the C-1 hydroxyl of sphingosine in glycosidic linkage rather than through a phosphodiester bond. The sugar donor is a UDP-sugar (UDP-glucose or UDP galactose).

FIGURE 21–31 Biosynthesis of sphingolipids. Condensation of palmitoyl-CoA and serine followed by reduction with NADPH yields sphinganine, which is then acylated to N-acylsphinganine (a ceramide). In animals, a double bond (shaded pink) is created by a mixed-function oxidase, before the final addition of a head group: phosphatidylcholine, to form sphingomyelin; glucose, to form a cerebroside.