Abou-Khalil S, Abou-Khalil W H, Whitney P L, Yunis A A
Department of Medicine, University of Miami School of Medicine, Fla.
Pharmacology. 1987;35(6):308-16. doi: 10.1159/000138355.
The amino acid pool of mitochondria has been recently implicated in the sensitivity of erythroid cells to chloramphenicol (CAP) [8]. In the present study, we have analyzed the composition of that pool in the sensitive erythroleukemia mitochondria (EM) and compared it with that of the resistant chloroma mitochondria (CM). We have also tested the effect of every major component in each pool on the sensitivity to CAP. The study of endogenous amino acid composition of EM and CM was performed with a JEOL 5AH amino acid analyzer, and the sensitivity to the drug was assayed by determining its interaction with the mitochondrial protein synthesis activity. Analysis of the total endogenous pool showed about 20% more amino acids in CM compared to EM. However, some amino acids were present in significantly higher (e.g. glycine, serine and histidine) or lower (e.g. proline, leucine, arginine, glutamic acid and threonine) quantity within EM. When compensating for each low amino acid in either CM or EM by addition of that particular acid to the incubation medium, only glycine and serine had a significant effect. Thus, the addition of glycine or serine enhanced the sensitivity to CAP from 14 to 49-52% in CM, but were without effect in EM. Addition of the other acids to either mitochondria gave little or no effect. Since serine could be interconvertible intramitochondrially to glycine, and because the latter with succinate are the first reactants in heme biosynthesis which is initiated inside the mitochondria, it would appear that erythroid cell sensitivity to CAP is predetermined by the mitochondrial glycine-serine pool and might be somehow related to the pathway of heme biosynthesis in these cells.
线粒体的氨基酸库最近被认为与红系细胞对氯霉素（CAP）的敏感性有关[8]。在本研究中，我们分析了敏感的红白血病线粒体（EM）中该氨基酸库的组成，并将其与耐药的绿色瘤线粒体（CM）的氨基酸库组成进行了比较。我们还测试了每个氨基酸库中每种主要成分对CAP敏感性的影响。使用JEOL 5AH氨基酸分析仪对EM和CM的内源性氨基酸组成进行了研究，并通过测定药物与线粒体蛋白质合成活性的相互作用来检测对该药物的敏感性。对总内源性氨基酸库的分析表明，与EM相比，CM中的氨基酸多约20%。然而，某些氨基酸在EM中的含量明显更高（如甘氨酸、丝氨酸和组氨酸）或更低（如脯氨酸、亮氨酸、精氨酸、谷氨酸和苏氨酸）。当通过向孵育培养基中添加特定氨基酸来补偿CM或EM中每种含量较低的氨基酸时，只有甘氨酸和丝氨酸有显著影响。因此，添加甘氨酸或丝氨酸可使CM对CAP的敏感性从14%提高到49 - 52%，但对EM没有影响。向任何一种线粒体中添加其他氨基酸几乎没有或没有影响。由于丝氨酸在线粒体内可与甘氨酸相互转化，并且因为甘氨酸与琥珀酸是线粒体内部启动的血红素生物合成中的首批反应物，所以红系细胞对CAP的敏感性似乎由线粒体甘氨酸 - 丝氨酸库预先决定，并且可能与这些细胞中的血红素生物合成途径以某种方式相关。
