Snyder Nathaniel W, Basu Sankha S, Worth Andrew J, Mesaros Clementina, Blair Ian A
Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104 A. J. Drexel Autism Institute, Drexel University, Philadelphia, PA 19104.
Department of Systems Pharmacology and Translational Therapeutics, University of Pennsylvania, Philadelphia, PA 19104.
J Lipid Res. 2015 Jan;56(1):142-50. doi: 10.1194/jlr.M055384. Epub 2014 Nov 25.
Metabolism of propionate involves the activated acyl-thioester propionyl-CoA intermediate. We employed LC-MS/MS, LC-selected reaction monitoring/MS, and LC-high-resolution MS to investigate metabolism of propionate to acyl-CoA intermediates. We discovered that propionyl-CoA can serve as a precursor to the direct formation of a new six-carbon mono-unsaturated acyl-CoA. Time course and dose-response studies in human hepatocellular carcinoma HepG2 cells demonstrated that the six-carbon mono-unsaturated acyl-CoA was propionate-dependent and underwent further metabolism over time. Studies utilizing [(13)C1]propionate and [(13)C3]propionate suggested a mechanism of fatty acid synthesis, which maintained all six-carbon atoms from two propionate molecules. Metabolism of 2,2-[(2)H2]propionate to the new six-carbon mono-unsaturated acyl-CoA resulted in the complete loss of two deuterium atoms, indicating modification at C2 of the propionyl moiety. Coelution experiments and isotopic tracer studies confirmed that the new acyl-CoA was trans-2-methyl-2-pentenoyl-CoA. Acyl-CoA profiles following treatment of HepG2 cells with mono-unsaturated six-carbon fatty acids also supported this conclusion. Similar results were obtained with human platelets, mouse hepatocellular carcinoma Hepa1c1c7 cells, human bronchoalveolar carcinoma H358 cells, and human colon adenocarcinoma LoVo cells. Interestingly, trans-2-methyl-2-pentenoyl-CoA corresponds to a previously described acylcarnitine tentatively described in patients with propionic and methylmalonic acidemia. We have proposed a mechanism for this metabolic route consistent with all of the above findings.
丙酸的代谢涉及活化的酰基硫酯丙酰辅酶A中间体。我们采用液相色谱 - 串联质谱法（LC-MS/MS）、液相色谱 - 选择反应监测/质谱法（LC-selected reaction monitoring/MS）和液相色谱 - 高分辨率质谱法（LC-high-resolution MS）来研究丙酸向酰基辅酶A中间体的代谢过程。我们发现丙酰辅酶A可作为直接形成一种新的六碳单不饱和酰基辅酶A的前体。在人肝癌HepG2细胞中进行的时间进程和剂量反应研究表明，这种六碳单不饱和酰基辅酶A依赖于丙酸，并会随着时间进一步代谢。利用[(13)C1]丙酸和[(13)C3]丙酸进行的研究提示了一种脂肪酸合成机制，该机制保留了来自两个丙酸分子的所有六个碳原子。2,2-[(2)H2]丙酸代谢为新的六碳单不饱和酰基辅酶A导致两个氘原子完全丢失，这表明丙酰部分的C2位发生了修饰。共洗脱实验和同位素示踪研究证实，新的酰基辅酶A是反式-2-甲基-2-戊烯酰辅酶A。用单不饱和六碳脂肪酸处理HepG2细胞后的酰基辅酶A谱也支持这一结论。在人血小板、小鼠肝癌Hepa1c1c7细胞、人支气管肺泡癌H358细胞和人结肠腺癌LoVo细胞中也获得了类似结果。有趣的是，反式-2-甲基-2-戊烯酰辅酶A与先前在丙酸血症和甲基丙二酸血症患者中初步描述的一种酰基肉碱相对应。我们已经提出了一种与上述所有发现一致的该代谢途径的机制。
