METABOLISM OF UNSATURATED FATTY AICDS

不饱和脂肪酸的代谢

• 批准号: 3246591
• 负责人: KOU-YI TSERNG
• 金额: $ 11.23万
• 依托单位: CASE WESTERN RESERVE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-05-01 至 1995-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3246591
• 关键词: NAD(H) phosphate; NAD(P) transhydrogenase; acyl coA dehydrogenases; aerobiosis; coenzyme A; enzyme activity; enzyme inhibitors; fatty acid metabolism; gas chromatography; hydrocarbon oxidoreductase; laboratory rat; mass spectrometry; mitochondria; oleate; oxidation reduction reaction; oxygen microelectrode; peroxisome; saturated /unsaturated bonds; stable isotope; unsaturated fatty acids

Recent studies have lead to a revised pathway for the oxidation of a cis-4 double bond to include a NADPH-dependent 2,4-dienoyl-CoA reductase step instead of the conventional epimerase pathway. Preliminary data obtained in our laboratory have indicated that the oxidation of a cis-5 double bond, encountered in the oxidation of odd-numbered double bond unsaturated fatty acids, is not through the conversion to a cis-3 enoyl-CoA, followed by isomerization to a trans-2-enoyl-CoA, as it appears in all biochemistry textbooks. Instead, it is through a direct reduction of the cis-5-enoyl-CoA to its saturated analogue via a NADPH-dependent pathway. Therefore, the oxidation of all unsaturated fatty acids requires a reduction step which in dependent on the availability of NADPH. In this proposal, we will study the existence of this reduction pathway in intact mitochondria and peroxisomes from rat liver and other organs. The reductase will be isolated and purified. This enzyme will be compared to 2,4-dienoyl-CoA reductase. In addition, he mechanism of reduction and the metabolic block of a cis-5 double bond to beta-oxidation will be studied with synthetic intermediates and with stable isotope labels. The effect of double bond on the oxidation of fatty acids will be studied with oxygen electrode and gas chromatograph-mass spectrometry. Also, these effects will be studied at enzyme level with acyl-CoA dehydrogenases, crotonases, and 3-hydroxyacyl-CoA dehydrogenases. Potential "mechanism-based" inhibitors to this reduction pathway will be investigated with analogues containing acetylene group. This newly revised pathway for the metabolism of unsaturated fatty acids explains the high activity of transhydrogenase, which converts NADP to NADPH, in heart cells where no significant synthetic function is known. In Addition, this reduction pathway might be an universal pathway for the metabolism of other cis-5 containing endogenous substrates, which include prostaglandins and related metabolites. The knowledge derived from this investigation will guide us in the evaluation of patients with inborn errors of fatty acid metabolism for a possible reductase deficiency. Whether the control of the reductase activity or the level of NADPH is related to cancer promotion or the beneficial effects on lipoproteins, attributed to unsaturated fatty acids, remains to be investigated.

最近的研究已经导致了一种修正的氧化途径， 顺式-4双键，包括NADPH依赖性2，4-二烯酰辅酶A还原酶 步骤，而不是传统的差向异构酶途径。 初步数据 在我们的实验室中获得的结果表明， 奇数双键氧化时遇到的双键 不饱和脂肪酸，是不是通过转化为顺式-3 烯酰-CoA，然后异构化为反式-2-烯酰-CoA，因为它 出现在所有生物化学教科书中。 相反，它是通过直接 将顺式-5-烯酰基-CoA通过还原酶还原成其饱和类似物， NADPH依赖性途径。 因此，所有不饱和的氧化 脂肪酸需要还原步骤， NADPH的可用性。 在本提案中，我们将研究这一还原途径的存在 在大鼠肝脏和其他器官的完整线粒体和过氧化物酶体中。 还原酶将被分离和纯化。 这种酶将 与2，4-二烯酰辅酶A还原酶相比。此外， 还原和代谢阻断顺式-5双键， 将用合成中间体和 稳定同位素标记。 研究了双键对氧化反应的影响 脂肪酸将用氧电极和气体进行研究 色谱-质谱法。 此外，这些影响将在 酰基辅酶A脱氢酶、巴豆酸酶和 3-羟酰基-CoA脱氢酶。 潜在的“机制型”抑制剂 将使用含有以下物质的类似物研究该还原途径： 乙炔基 这种新修订的不饱和脂肪酸代谢途径 解释了转氢酶的高活性，它将NADP转化为 NADPH，在心脏细胞中，没有已知的重要合成功能。 此外，这种还原途径可能是一种普遍的途径， 其它含顺式-5的内源性底物的代谢，包括 野牡丹素及其相关代谢物。 从这方面获得的知识 这项研究将指导我们对先天性心脏病患者的评估。 脂肪酸代谢的错误，可能是还原酶缺乏。 无论是还原酶活性的控制还是NADPH水平的控制， 与癌症促进或对脂蛋白的有益作用有关， 归因于不饱和脂肪酸，仍有待研究。