《厦大生化》PPT课件.ppt

1、Chapter 26 The biosynthesis of membrane lipids and steroids,Fats such as the triacylglycerol molecule are wildly used to store excess energy for later use and to fulfill other purposes.,26.1 Phosphatidate is a common intermediate in the synthesis of phospholipids and triacylglycerols,Glycerol phosph

2、ate acyltransferase.,Endoplasmic reticulum / Outer mitochondrial membrane.,Diglyceride acyltransferase.,Triacylglcerol synthetase complex in liver.,26.1.1 The synthesis of phospholipids requires an activated intermediate,Phospholipid synthesis = the combination of a diacylglyceride with an alcohol A

3、nabolic reaction Diacylglycerol or alcohol should be activated.,Synthesis from an activated diacylglerol,Structure of CDP-diacylglycerol.,Synthesis form an activated alcohol,In all of biosyntheses, an activated intermediate (UDP-glucose, CDP-diacylglycerol, CDP-alcohol) is formed from a phosphorylat

4、ed substrate (glucose-1-phosphate, phosphatide, phosphorylalcohol) and a nucleoside triphosphate. The activated intermediate then reacts with a hydroxyl group (the terminus of glycogen, the side chain of serine, or a diacylglycerol).,26.1.2 Plasmalogens and other ether phospholipids are synthesized

5、from dihydroxyacetone phosphate,Synthesis of an ether phospholipid.,26.1.3 Sphingolipids are synthesized from ceramide,鞘氨醇,Synthesis of sphingolipids.,神经酰胺,葡萄糖脑苷脂,神经节 苷脂,鞘磷脂,Ganglioside GM1.,半乳糖,唾液酸,N-乙酰半乳糖胺,葡萄糖,26.1.4 Respiratory distress syndrome and Tay-Sachs disease result from the disruption of

6、 lipid metabolism,Tay-Sachs disease （泰萨氏幼年黑朦白痴症） (1) A 1-year-old infant with Tay-Sachs disease. (2) Electron micrograph of a portion of an affected brain cell, showing the abnormal ganglioside deposits in the lysosomes.,26.2 Cholesterol is synthesized from acetyl coenzyme A in three stages,Labeling

7、 of cholesterol.,26.2.1 The synthesis of mevalonate, which is activated as isopentenyl pyrophosphate, initiates the synthesis of cholesterol,Fates of 3-hydroxy-3-methylglutaryl CoA.,二羟甲基戊酸,Synthesis of isopentenyl pyrophosphate.,Squalene synthesis.,异戊二烯 基转移酶,焦磷酸 牻牛儿酯,26.2.2 Squalene cyclizes to form

8、 cholesterol,Squalene cyclization.,Oxidosqualene cyclase. Cholesterol formation.,26.3 The complex regulation of cholesterol biosynthesis takes place at several levels,HMG-CoA reductase.,3-hydroxy-3-methylglutaryl CoA reductae The synthesis of reductase mRNA is controlled by sterol regulatory element

9、 binding protein. The translation of reductase mRNA. The degradation of the reductase. Phosphorylation decrease the activity of the redutase.,26.3.1 Lipoproteins transport cholesterol and triacylglycerols throughout the organism,The vesicle in liver that is releasing VLDL particle.,The LDL particle

10、(22 nm),26.4 Important derivatives of cholesterol include bile salts and steroid hormones.,Synthesis of bile salts.,孕烯醇酮,孕酮,睾丸酮,皮质醇,皮质酮,醛固酮,雌二醇,26.4.1 Pregnenolone, a precursor for many other steroids, is formed from cholesterol by cleavage of its side chain,孕烯醇酮,26.4.2The synthesis of progesterone

11、and corticosteroids from pregnenolone,Pathways for the formation of progesterone, cortisol, and aldosterone.,孕酮,26.4.5 The synthesis of androgens and estrogens from pregnenolone,Pathways for the formation for androgens and estrogens,26.4.6 Vitamin D is derived from cholesterol by the ring-splitting activity of light,Key terms,Pho