Aw T Y, Jones D P
Am J Physiol. 1985 Nov;249(5 Pt 1):C385-92. doi: 10.1152/ajpcell.1985.249.5.C385.
The activities of two ATP-requiring systems with different subcellular localizations were studied in cells in which average cellular ATP concentration was varied. The cytosolic ATP-sulfurylase activity varied linearly with the cellular ATP concentration; however, the plasma membrane Na+-K+-ATPase was substantially more sensitive to decreased ATP concentration. Under conditions where the cellular ATP concentration was lowered to 40% of control, Rb+ uptake was nearly zero. The results indicate that ATP-utilizing enzymes located in the plasma membrane in liver cells are exposed to a lower ATP concentration than are enzymes present in the cytosolic fluid surrounding the mitochondria. Analysis of radial diffusion of ATP from mitochondria, assuming that mitochondria are spherical and ATP consumption is zero order in ATP concentration, shows that the average ATP supply radius decreases as mitochondrial ATP production decreases. Hence, during limited ATP supply, enzymes with a greater average distance from mitochondria (e.g., plasma membrane ATPases) experience a more dramatic decrease in ATP concentration than enzymes in close proximity to mitochondria (e.g., cytoplasmic enzymes). Thus microheterogeneity of ATP supply can occur in cells without membranal compartmentation due to nonuniform distribution of ATP-generating and ATP-consuming systems.
在平均细胞ATP浓度发生变化的细胞中，研究了两种具有不同亚细胞定位且需要ATP的系统的活性。胞质ATP硫酸化酶活性随细胞ATP浓度呈线性变化；然而，质膜Na⁺-K⁺-ATP酶对ATP浓度降低更为敏感。在细胞ATP浓度降至对照的40%的条件下，Rb⁺摄取几乎为零。结果表明，肝细胞质膜中的ATP利用酶所接触的ATP浓度低于线粒体周围胞质液中的酶。假设线粒体为球形且ATP消耗对ATP浓度呈零级反应，对ATP从线粒体的径向扩散进行分析表明，随着线粒体ATP生成减少，平均ATP供应半径减小。因此，在ATP供应有限期间，距线粒体平均距离更大的酶（如质膜ATP酶）比靠近线粒体的酶（如细胞质酶）经历更显著的ATP浓度下降。因此，由于ATP生成和消耗系统的分布不均，在没有膜分隔的细胞中可能会出现ATP供应的微异质性。
