三羧酸循环（TCA 循环）
中文名称
通路描述
三羧酸循环（TCA 循环， Krebs 循环）是碳水化合物和脂肪酸氧化最终步骤的重要有氧途径。循环始于乙酰辅酶 A，即乙酸（来自糖酵解和丙酮酸氧化）的活化形式，以及脂肪酸的β氧化。乙酰辅酶 A 中的两碳乙酰基转移到四碳化合物草酰乙酸形成六碳化合物草酰乙酸。在一系列反应中，草酰乙酸中的两碳被氧化为 CO2，该反应途径为氧化磷酸化和其他代谢过程提供 NADH。该途径还提供重要的代谢前体，包括 2-氧代丁酸。在循环结束时，剩余的四个碳部分转化回草酰乙酸。根据基因组序列数据，许多生物似乎缺乏完整循环的基因 [MD:M00009]，但包含特定段落的基因 [MD:M00010 M00011]。
英文描述
The citrate cycle (TCA cycle, Krebs cycle) is an important aerobic pathway for the final steps of the oxidation of carbohydrates and fatty acids. The cycle starts with acetyl-CoA, the activated form of acetate, derived from glycolysis and pyruvate oxidation for carbohydrates and from beta oxidation of fatty acids. The two-carbon acetyl group in acetyl-CoA is transferred to the four-carbon compound of oxaloacetate to form the six-carbon compound of citrate. In a series of reactions two carbons in citrate are oxidized to CO2 and the reaction pathway supplies NADH for use in the oxidative phosphorylation and other metabolic processes. The pathway also supplies important precursor metabolites including 2-oxoglutarate. At the end of the cycle the remaining four-carbon part is transformed back to oxaloacetate. According to the genome sequence data, many organisms seem to lack genes for the full cycle [MD:M00009], but contain genes for specific segments [MD:M00010 M00011].
所含基因
30 个基因