Fontaine E M, Keriel C, Lantuejoul S, Rigoulet M, Leverve X M, Saks V A
Laboratoire de Bioénergétique, Université Joseph Fourier, Grenoble, France.
Biochem Biophys Res Commun. 1995 Aug 4;213(1):138-46. doi: 10.1006/bbrc.1995.2108.
The kinetics of regulation mitochondrial respiration by external ADP in permeabilized hepatocytes was studied further. In digitonin-permeabilized hepatocytes, the apparent Km for ADP in regulation of respiration was decreased from 275 +/- 35 microM in control to 48 +/- 8 microM by a treatment with trypsin (15 min, 0.125 mg/ml). In liver tissue homogenates, trypsin treatment similarly decreased the Km value for ADP. These results show that ADP diffusion in hepatocytes may be retarded due to some unknown cytoplasmic trypsin-sensitive protein factor(s) which may be lost during isolation of mitochondria. Since we have previously reported a limited permeability of the outer mitochondrial membrane in isolated hepatocytes (Saks et al. 1995, Biochem. Biophys. Res. Commun., 208, 919-926), we conclude that an important site of control of respiration in liver cells in vivo is located at the porin channels of the outer mitochondrial membrane.
对通透化肝细胞中外部ADP调节线粒体呼吸的动力学进行了进一步研究。在用洋地黄皂苷通透化的肝细胞中，通过胰蛋白酶处理（15分钟，0.125毫克/毫升），ADP调节呼吸的表观Km值从对照中的275±35微摩尔降至48±8微摩尔。在肝组织匀浆中，胰蛋白酶处理同样降低了ADP的Km值。这些结果表明，肝细胞中ADP的扩散可能因某些未知的细胞质胰蛋白酶敏感蛋白因子而受阻，这些因子可能在分离线粒体的过程中丢失。由于我们之前报道过分离的肝细胞中外膜线粒体膜的通透性有限（萨克斯等人，1995年，《生物化学与生物物理研究通讯》，208，919 - 926），我们得出结论，体内肝细胞呼吸控制的一个重要位点位于外膜线粒体膜的孔蛋白通道。
