Cohen N S, Kuda A
Department of Biochemistry and Molecular Biology, University of Southern California School of Medicine, Los Angeles, 90033, USA.
J Cell Biochem. 1996 Mar 1;60(3):334-40. doi: 10.1002/(SICI)1097-4644(19960301)60:3%3C334::AID-JCB5%3E3.0.CO;2-X.
Argininosuccinate synthetase and argininosuccinate lyase are soluble cytoplasmic enzymes of the urea cycle. Previous biochemical studies using permeabilized hepatocytes showed that these enzymes are organized in situ, and function as if they are located next to the outer membrane of mitochondria. We have now confirmed and extended those observations in intact liver by means of immunocytochemistry at the electron microscope level. Morphometric analysis of the electron micrographs shows that argininosuccinate synthetase and argininosuccinate lyase are located in the immediate vicinity of the mitochondria, predominantly next to the cytoplasmic surface of the outer membrane. Some immuno-specific protein is also observed in the endoplasmic reticulum in the immediate vicinity of the mitochondria. These results support our previous biochemical findings, and additionally suggest that virtually all of the argininosuccinate synthetase and argininosuccinate lyase of the liver parenchymal cell are located just outside the mitochondria.
精氨琥珀酸合成酶和精氨琥珀酸裂解酶是尿素循环中的可溶性细胞质酶。先前使用通透化肝细胞进行的生化研究表明，这些酶在原位是有组织的，并且其功能就好像它们位于线粒体外膜附近。我们现在通过电子显微镜水平的免疫细胞化学在完整肝脏中证实并扩展了这些观察结果。电子显微镜照片的形态计量分析表明，精氨琥珀酸合成酶和精氨琥珀酸裂解酶位于线粒体的紧邻区域，主要位于外膜的细胞质表面附近。在紧邻线粒体的内质网中也观察到一些免疫特异性蛋白。这些结果支持了我们先前的生化发现，并且还表明肝实质细胞中几乎所有的精氨琥珀酸合成酶和精氨琥珀酸裂解酶都位于线粒体外。
