METABOLISM OF ACYLGLYCEROLS AND （酰基甘油代谢和）.pdfVIP

METABOLISM OF ACYLGLYCEROLS AND SPHINGOLIPDS Ben S. Ashok MSc.,FAGE.,PhD., Dept. of Biochemistry STORAGE AND MEMBRANE LIPIDS STORAGE LIPIDS • Mainly as triacylglycerols (triglycerides) in adipose cells • Constitute 84% of stored energy • Protein - 15% • Carbohydrate (glucose or glycogen) - 1% MEMBRANE LIPIDS PHOSPHOLIPIDS, GLYCOLIPIDS CLASSIFICATION OF PHOSPHOLIPIDS Depending on the type of alcohol, PL are classified into two groups • Phosphoglycerides • Sphingophospholipids • Phosphatidate • Sphingomyelins • Lysophosphatidate • Phosphatidyl choline • Phosphatidyl ethanolamine • Phosphatidyl serine • Phosphatidyl inositol • Phosphatidyl glycerol • Diphosphatidyl glycerol GLYCEROPHOSPHOLIPIDS Glycerophospholipids are membrane lipids in which 2 fatty acids are attached in ester linkage to the first and second carbons of glycerol. A highly polar alcohol is attached through a phosphodiester linkage to the third carbon. BIOSYNTHESIS OF MEMBRANE PHOSPHOLIPIDS • Synthesis of the backbone molecule (glycerol or sphingosine). • Attachment of fatty acids to the backbone in ester or amide linkage. • Addition of a hydrophilic head group joined to the backbone through a phosphodiester linkage. • In some cases, alteration or exchange of the head group to yield the final phospholipid product. TRIACYLGLYCEROLS AND GLYCEROPHOSPHOLIPIDS ARE SYNTHESIZED FROM THE SAME PRECURSORS Formation of Glycerol-3-phosphate: Fatty acyl groups are activated by formation of fatty acyl- CoA. Then they are transferred to ester linkage with glycerol-3-