Abstract

The dynamics of the activity of glutamate dehydrogenase (GDH, EC 1.4.1.2) during germination in corn leaves and scutes has been studied. It was found that changes in its activity are due to biochemical and molecular aspects of enzyme functioning. This was confirmed in a study of the relative level of transcripts of the gdh-1 and gdh-2 genes, which encode GDH subunits. It was shown that this enzyme in leaves is mainly localized in mitochondria (86.54%) and, to a lesser extent, cytosol (9.53%) and chloroplasts (3.92%). Four-stage purification made it possible to isolate three GDH enzyme preparations from corn leaves with different purification levels. One form (GDH1) was purified to a specific enzyme-preparation activity of 195 U/mg protein with a purification rate of 98 times and a yield of 8%. The second form (GDH2) was obtained with a specific activity of 166 U/mg protein, a purification rate of 83 times, and a yield of 32%. The GDH3 preparation had a specific activity of 122.2 U/mg protein, a purification rate of 61 times, and a yield of 21%. The pH optimum was determined from the amination reaction. The optimal pH values are 7.5 for GDH1 and 7.0 and 8.5 for GDH2 and GDH3, respectively. The obtained GDH isoforms have different Km values for 2‑oxoglutarate: 0.34 mM for GDH1 and 0.6 mM and 0.22 mM, respectively, for GDH2 and GDH3.

中文翻译：

---

玉米玉米中谷氨酸脱氢酶同工型的催化和分子方面

摘要

研究了玉米叶片和根茎萌发过程中谷氨酸脱氢酶（GDH，EC 1.4.1.2）活性的动态。发现其活性的变化归因于酶功能的生化和分子方面。一项关于gdh-1和gdh-2转录本相对水平的研究证实了这一点。基因，编码GDH亚基。结果表明，叶片中的这种酶主要定位于线粒体（86.54％），较小程度地位于胞质溶胶（9.53％）和叶绿体（3.92％）。四阶段纯化使从纯化水平不同的玉米叶片中分离出三种GDH酶制剂成为可能。将一种形式（GDH1）纯化至195 U / mg蛋白的特定酶制备活性，纯化率为98倍，产率为8％。获得第二种形式（GDH2），其比活为166 U / mg蛋白，纯化率为83倍，产率为32％。GDH3制剂的比活为122.2 U / mg蛋白，纯化率为61倍，产率为21％。由胺化反应确定最适pH。对于GDH1，最佳pH值是7.5，对于GDH2和GDH3，最佳pH值是7.5和8.5，分别。所获得的GDH同工型对2-氧代戊二酸的Km值不同：GDH1为0.34 mM，GDH2和GDH3分别为0.6 mM和0.22 mM。