壳聚糖对不结球白菜叶片氮代谢关键酶的调节作用

Regulation of Chitosan on the Key Enzymes of Nitrogen Metabolism in Non-Heading Chinese Cabbage Leaves

研究了壳聚糖(chitosan)对氮代谢关键酶[谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)和谷氨酸脱氢酶(GDH)]和可溶性蛋白质含量的影响。结果表明:0.8mg·mL^(-1)壳聚糖溶液喷洒不结球白菜叶片后,GS对NH_4^+的K_M值增大,而GDH对NH_4^+的K_M值变小;在酶活性检测中,GS比活性受到了抑制,而GDH比活性则被提高,GOGAT比活性则表现为先上升后下降;削弱了不结球白菜叶片中的氨同化过程的GS-GOGAT途径,加强了GDH途径;同时,提高了叶片可溶性蛋白含量。

The effects of chitosan on the key enzymes (glutamine synthetase, GS; glutamine 2 -oxoglutarate aminotransferase, GOGAT; glutamate dehydrogenase, GDH) in nitrogen etabolism and the protein content were investigated in non -heading Chinese Cabbage leaves. The results showed that the chitosan treatment led to depression of GS and activation of GDH after the leaves were spayed with chitosan (0.8 mg/mL). The Km of GDH for ammonium ion was lower and that of GS was higher in the chitosan-treated leaves than that in the chitosan-untreated leaves. Analysis of the ratios of GS/GDH and GS/GOGAT displayed that GDH was predominant in ammonium assimilation, but GS-GOGAT cycle was secondary. The lowering of the KM of GDH for ammonium ion implied that the ammination capability of the non-heading Chinese Cabbage leaves was enhanced. The enhanced ammination activity of GDH would in turn lead to increase of soluble protein content.