Orlický J, Ruscák M, Ruscáková D, Hager H
Physiol Bohemoslov. 1981;30(4):323-8.
The activity of certain key enzymes involved in glutamic acid metabolism was studied in purified brain mitochondria and in mitochondrial subfractions separated in a discontinuous 1.2--1.6 mol/l sucrose gradient. Alanine aminotransferase and glutamate dehydrogenase were found to be matrix enzymes and aspartate aminotransferase to be associated with the inner mitochondrial membranes. After the purified mitochondria had been separated into 5 subfractions, aspartate aminotransferase and NAD+-dependent isocitrate dehydrogenase were found to be bound to the lighter mitochondrial subfractions settling at the 1.4--1.5 mol/l sucrose boundary while alanine aminotransferase, 4-aminobutyrate transaminase and glutamate dehydrogenase were associated with the heavier subfractions settling below 2.4 mol/l sucrose. The highest specific activity of the given enzymes was found in the subfraction settling at the 1.4--1.5 mol/l sucrose boundary, the only exception being alanine aminotransferase activity, whose maximum was found in the subfractions settling in 1.5 and 1.6 mol/l sucrose. It was concluded that alanine aminotransferase, in conjunction with glutamate dehydrogenase, is linked to NH3 binding and to the oxidation of reduced adenine nucleotides; in addition, alanine aminotransferase is presumed to have the function of transporting glutamate from the mitochondria to the extramitochondrial space.
在纯化的脑线粒体以及通过不连续的1.2 - 1.6 mol/l蔗糖梯度分离得到的线粒体亚组分中，研究了参与谷氨酸代谢的某些关键酶的活性。发现丙氨酸转氨酶和谷氨酸脱氢酶是基质酶，而天冬氨酸转氨酶与线粒体内膜相关。在将纯化的线粒体分离成5个亚组分后，发现天冬氨酸转氨酶和NAD⁺依赖性异柠檬酸脱氢酶与沉降在1.4 - 1.5 mol/l蔗糖边界处的较轻线粒体亚组分结合，而丙氨酸转氨酶、4-氨基丁酸转氨酶和谷氨酸脱氢酶与沉降在2.4 mol/l蔗糖以下的较重亚组分相关。在所研究的酶中，最高比活性出现在沉降在1.4 - 1.5 mol/l蔗糖边界处的亚组分中，唯一的例外是丙氨酸转氨酶活性，其最大值出现在沉降在1.5和1.6 mol/l蔗糖中的亚组分中。得出的结论是，丙氨酸转氨酶与谷氨酸脱氢酶一起，与NH₃结合以及还原型腺嘌呤核苷酸的氧化有关；此外，推测丙氨酸转氨酶具有将谷氨酸从线粒体转运到线粒体外空间的功能。
