Applications Of GLS And γ-GGT For The Syntheses Of Theanine

L-theanine, a unique amino acid found almost exclusively in tea plants, is tea exceptional taste substances, widely used in medical, health care, food fields. In recent years, it has been reported that theanine has many favorable effects, such as lower blood pressure, anti-cancer, neuroprotection, enhancing memory, etc. The preparation of L-theanine has several methods, such as:separation and extraction from tea, chemical synthesis and biosynthesis. Considering product costs, product safety and product quality, biosynthesis is the preparation of L-theanine development trend. And because the advantages of low cost, short cycle, microbial enzymatic synthesis become the most potential preparation method, owing the bright prospect. Now, there are several kinds of enzymes which catalyze the biosynthesis of theanine:theanine synthetase, glutamine synthetase, y-glutamylmethylamide synthetase, glutaminase and y-glutamyltranspeptidase. The main purpose of this experiment is to optimize the glutaminase and y-glutamyltranspeptidase peptide enzyme-catalyzed synthesis of L-theanine conditions, to improve the rate of substrate conversion of glutamine,and to lay the foundation of use of microbial fermentation industrial production theanine in the further. The main findings are as follows:1. Optimizing the glutaminase peptide enzyme-catalyzed synthesis of L-theanine conditions by L-glutamine and ethylamine. Incubation at46℃for6h in4mL reaction system (0.3M glutamine,1.8Methylamine,2Utransfer crude extract, pH9.8), theanine synthesis reaches the highest point. However, the The HPLC measurement result display that even under the optimal reaction conditions, glutamine Enzymatic Synthesis of L-theanine yield was just0.239g/L. This is far from the purpose of Industrial production of theanine, and the specific reasons remains to be further analyzed.2. Optimizing the y-glutamyltranspeptidase peptide enzyme-catalyzed synthesis of L-theanine conditions by L-glutamine and ethylamine, and Improving The/Gln substrate conversion rate. Incubation at37℃for36h in500mL reaction system (0.2M glutamine,3Utransfer crude extract,0.06M NH4HCO3,1mM Mg2(OH)2CO3, pH9.8), the yield of theanine is26.45g/L and the substrate conversion rate is up to86%. It provides broad prospects for future industrial production of L-theanine.