第二节 脂肪酸的合成代谢(-11-2)第二节 脂肪酸的合成代谢(5-11-2)第二节 脂肪酸的合成代谢(5-11-2)第二节 脂肪酸的合成代谢(5-11-2).ppt

细胞内进行 部位 动 物 植 物 线粒体 叶绿体、前质体 ACP 内质网 电子供体 脂酰基的载体 二碳单位的供体 内质网 NADPH 丙二酸单酰CoA 不 明 确 NADH NADPH CoA 乙酰CoA 丙二酸单酰CoA CoA NADPH 2. 脂肪酸碳链的延长过程 (二) 脂肪酸碳链的延长 二. 脂肪酸的合成 第二节 脂肪酸的合成代谢 一. 甘油的合成 由糖酵解的中间产物磷酸二羟丙酮还原而成。 甘油的合成在细胞质中进行。? 事实上，在甘油和脂肪酸缩合连结成脂肪时，所需要的是3-磷酸甘油，而不是游离的甘油。 (一) 脂肪酸的从头合成 二. 脂肪酸的合成 原料：乙酰CoA? 产物：不超过16碳的饱和脂肪酸 部位： 动物体 —— 细胞质 植物体 —— 叶绿体和前质体? Overview Fatty acids are synthesized by the condensation of two-carbon units. However, in terms of the enzymic steps involved, the process is not the reversed of ?-oxidation. Fatty acid synthesis involves a separate series of reactions to build up long-chain hydrocarbons from acetyl CoA units. The key differences between fatty acid synthesis and breakdown are: ? (一) 脂肪酸的从头合成 二. 脂肪酸的合成 1.?fatty acid synthesis occurs in the cytosol of both prokaryotes and eukaryotes whereas their degradation occurs in the mitochondria of eukaryotes; 2.?fatty acid synthesis uses NADPH as the reductant whereas NADH is produced in ?-oxidation; 3.?during their synthesis, fatty acids are covalently linked to an acyl carrier protein (ACP), as opposed to CoA in their degradation; 4.?the enzyme activities of fatty acid synthesis in higher organisms are present in a single polypeptide chain called fatty acid synthase, whereas in ?-oxidation the individual activities are present on separate enzymes. (一) 脂肪酸的从头合成 二. 脂肪酸的合成 1. 脂肪酸从头合成的过程 (一) 脂肪酸的从头合成 二. 脂肪酸的合成 (1) 乙酰CoA的来源和转运 Transport into the cytosol Fatty acids are synthesized in the cytosol, but acetyl CoA is produced from pyruvate in the mitochondria. Thus the acetyl CoA must be transferred from the mitochondria into the cytosol to allow fatty acid synthesis to occur. However, the inner mitochondrial membrane is not readily permeable to this molecule. This problem is overcome by the condensation of acetyl CoA with oxaloacetate to form citrate. 1. 脂肪酸从头合成的过程 (一) 脂肪酸的从头合成 二. 脂肪酸的合成 (1) 乙酰CoA的来源和转运 因为乙酰CoA在线粒体产生，乙酰CoA不能直接穿过线粒体内膜，需要通过“柠檬酸穿梭”的方式从线粒体基质到达细胞质，才能用于合成脂肪酸。 (一) 脂肪酸的从