Brass E P, Ruff L J
Department of Medicine, Case Western Reserve University, Cleveland, OH 44106.
J Nutr. 1992 Nov;122(11):2094-100. doi: 10.1093/jn/122.11.2094.
Coenzyme A without an acyl-thioester (CoASH) is required for numerous cellular reactions, and sequestration of CoASH as acyl-CoAs may impair metabolic function. Increased total CoA protects the cell from acyl-CoA accumulation, and enhanced CoA biosynthesis may represent a compensatory response in metabolic disease. To test the hypothesis that cellular CoA is redistributed from the cytosol to the mitochondria in response to mitochondrial acyl-CoA accretion, the subcellular distribution of hepatic CoA was determined by differential centrifugation and measurement of the mitochondrial marker enzyme citrate synthase. Liver from control, clofibrate-treated and hydroxycobalamin[c-lactam] (HCCL)-treated rats were used. Clofibrate increased total hepatic CoA concentration 2.2-fold, whereas HCCL (which causes inhibition of L-methylmalonyl-CoA mutase and consequent propionyl- and methylmalonyl-CoA accumulation) increased it threefold. However, clofibrate did not affect the percentage of total CoA in the mitochondria (control: 44 +/- 3%, clofibrate: 49 +/- 5%), and HCCL-treatment induced a marked redistribution of CoA into the mitochondria (HCCL: 78 +/- 8%). Redistribution of total CoA was also induced acutely by incubation of hepatocytes from control rats with 10 mmol/L propionate. Thus, redistribution of the cellular CoA pool can help maintain CoASH availability as mitochondrial acyl-CoA accumulation occurs and may be an important compensatory response to metabolic injury.
许多细胞反应都需要没有酰基硫酯的辅酶A（CoASH），而CoASH以酰基辅酶A的形式被隔离可能会损害代谢功能。总辅酶A增加可保护细胞免受酰基辅酶A积累的影响，而增强的辅酶A生物合成可能代表代谢疾病中的一种代偿反应。为了验证细胞辅酶A会因线粒体酰基辅酶A增加而从细胞质重新分布到线粒体的假说，通过差速离心和测量线粒体标记酶柠檬酸合酶来确定肝脏辅酶A的亚细胞分布。使用来自对照、氯贝丁酯处理和羟钴胺[γ-内酰胺]（HCCL）处理大鼠的肝脏。氯贝丁酯使肝脏总辅酶A浓度增加了2.2倍，而HCCL（它会抑制L-甲基丙二酰辅酶A变位酶并导致丙酰辅酶A和甲基丙二酰辅酶A积累）使其增加了3倍。然而，氯贝丁酯并不影响线粒体中总辅酶A的百分比（对照：44±3%，氯贝丁酯：49±5%），而HCCL处理导致辅酶A明显重新分布到线粒体中（HCCL：78±8%）。用10 mmol/L丙酸盐孵育对照大鼠的肝细胞也可急性诱导总辅酶A的重新分布。因此，随着线粒体酰基辅酶A积累，细胞辅酶A池的重新分布有助于维持CoASH的可用性，并且可能是对代谢损伤的一种重要代偿反应。
