200 results about "Glutamate dehydrogenase" patented technology

Transgenic plants containing free amino acids, particularly at least one amino acid selected from among glutamic acid, asparagine, aspartic acid, serine, threonine, alanine and histidine accumulated in a large amount, in edible parts thereof, and a method of producing them are provided. In this method, glutamate dehydrogenase (GDH) gene is introduced into a plant together with a regulator sequence suitable for over expressing the sequence encoding GDH gene in plant cells.

The invention discloses a method for preparing L-glufosinate-ammonium by use of amino acid dehydrogenase. The method comprises the following steps: taking 2-carbonyl-4-(hydroxymethylphosphonyl)butyric acid or a salt thereof as a substrate, taking a cell of the isolated glutamate dehydrogenase or in vitro expression glutamate dehydrogenase as a catalyst to perform reductive amination reaction under the condition of the existence of inorganic amino donor and reduced coenzyme, thereby acquiring the L-glufosinate-ammonium. The method disclosed by the invention is high in raw material conversion rate and high in yield, the product is easy to separate and purify, and the chirality purity is high; compared with the transaminase and like catalysis technology, the process is relatively simple, and the raw material conversion rate reaches up to 100%.

The instant invention is drawn to the methods and compositions necessary to provide recombinant proteins with a substantially reduced or eliminated content of norleucine or other non-standard amino acids. Various embodiments of the invention provide for the substantial elimination of the incorporation of non-standard amino acids into recombinant proteins by the co-expression or enhanced expression of a protein (or the enzymatically active portion thereof) capable of degrading norleucine or other non-standard amino acids, including norvaline, beta-methylnorleucine, and homoisoleucine. In certain particular embodiments of the invention, the norleucine is degraded by a glutamate dehydrogenase, a leucine dehydrogenase, a valine dehydrogenase, a phenylalanine dehydrogenase, a glutamate / leucine / phenylalanine / valine dehydrogenase, or an opine dehydrogenase. Also provided are the cells and DNA constructs for carrying out these methods.

A non-naturally occurring microbial organism has at least one exogenous nucleic acid encoding a MEK pathway enzyme expressed in a sufficient amount to produce MEK. The MEK pathway includes an enzyme selected from an acetoacetyl-CoA dehydrogenase (bifunctional), an acetoacetyl-CoA aldehyde dehydrogenase, a 3-oxobutyraldehyde reductase, a 3-oxobutanol dehydratase, an MEK oxidoreductase, a 3-oxobutyraldehyde aminotransferase, a 4-aminobutan-2-one deaminase, a 2-amino-4-ketopentanoate (AKP) thiolase, an AKP aminotransferase, a 2,4-dioxopentanoate decarboxylase, an AKP deaminase, an acetylacrylate decarboxylase, an AKP decarboxylase, a glutamate dehydrogenase, a 3-oxobutyraldehyde oxidoreductase (aminating) and an AKP oxidoreductase (aminating). A 2-butanol pathway further includes an MEK reductase. A method for producing MEK or 2-butanol includes culturing these organisms under conditions and for a sufficient period of time to produce MEK or 2-butanol.

A genetically engineered bacterium producing 2-phenylethanol and an applying method thereof are disclosed. The recombinant bacterium is constructed by coexpressing aromatic amino acid aminotransferase and exogenous phenylpyruvate decarboxylase (Aro10) (or indole-3-pyruvic acid decarboxylase), phenylethanol dehydrogenase or phenylacetaldehyde reductase in escherichia coli to obtain the recombinant bacterium producing the 2-phenylethanol. Glutamate dehydrogenase is coexpressed on this basis to achieve self-balancing cofactor circulation, thus increasing the yield of the 2-phenylethanol. The conversion ratio of the 2-phenylethanol prepared through the recombinant bacterium is high. The bacterium and the method have important application value in production of the 2-phenylethanol in the future.

A non-naturally occurring microbial organism has at least one exogenous nucleic acid encoding a MEK pathway enzyme expressed in a sufficient amount to produce MEK. The MEK pathway includes an enzyme selected from an acetoacetyl-CoA dehydrogenase (bifunctional), an acetoacetyl-CoA aldehyde dehydrogenase, a 3-oxobutyraldehyde reductase, a 3-oxobutanol dehydratase, an MEK oxidoreductase, a 3-oxobutyraldehyde aminotransferase, a 4-aminobutan-2-one deaminase, a 2-amino-4-ketopentanoate (AKP) thiolase, an AKP aminotransferase, a 2,4-dioxopentanoate decarboxylase, an AKP deaminase, an acetylacrylate decarboxylase, an AKP decarboxylase, a glutamate dehydrogenase, a 3-oxobutyraldehyde oxidoreductase (aminating) and an AKP oxidoreductase (aminating). A 2-butanol pathway further includes an MEK reductase. A method for producing MEK or 2-butanol includes culturing these organisms under conditions and for a sufficient period of time to produce MEK or 2-butanol.

The invention relates to a kit for diagnosing / measuring glycine by utilizing the technologies of the enzymic colorimetry and the enzyme linked immunosorbent assay. The invention further relates to a method, a principle and the composition and the components of a reagent for measuring the concentration of the glycine, and belongs to the technical field of medical / food inspection and measurement. The main components of the kit include a buffer solution, coenzyme, a 2-ketoglutaric acid, glycine aminotransferase, glutamate dehydrogenase and a stabilizer. Through mixing a sample and the reagent by a certain volume ratio, a series of enzymatic reactions occur, then the reactant is placed under an ultraviolet / visible light analyzer, and the degree / velocity of the increase in absorbance at 340 nm of the dominant wavelength is detected, thereby measuring the active concentration of the glycine.

This invention relates to a test kit for diagnosing hepatic and biliary diseases. The test kit has such advantages as high stability, high accuracy and high sensitivity. The test kit comprises two reagents. Reagent 1 comprises oxidized thio coenzyme, buffer solution, preservative, and anti-interference agent. Reagent 2 comprises 3alpha-HSD, reduced coenzyme, buffer solution, preservative, complexing agent, polymer accelerator, stabilizer, and one of formate dehydrogenase-formic acid-NAD, glutamate dehydrogenase-glutamic acid-oxidized nicotinamide coenzyme, glucose-6-phosphate dehydrogenase-glucose-oxidized nicotinamide coenzyme, glucose dehydrogenase-xylose-oxidized nicotinamide coenzyme, lactate dehydrogenase-alpha-ketoglutarate-oxidized nicotinamide coenzyme, and glycerol dehydrogenase-ethylene glycol-oxidized nicotinamide coenzyme.

The invention relates to promoters of the genes glutamate dehydrogenase, beta-acetylhexosaminidase and gamma-actin and their use in systems of expression, secretion and anti-sense of filamentary fungi. The invention also relates to the use of the promoters of the genes which code: (I) glutamate dehydrogenase NADP depending (EC.1.4.1.4) of Penicillium chrysogenum, (II) gamma-N-actylhexosaminidase (EC.3.2.1.52) of Penicillium chrysogenum and (III) gamma-actin of Penicillium chrysogenum and Acrimonium chrysogenum, which can be used for the construction of potent vectors of expression and secretion useful both for P. chrysogenum and for A. chrysogenum and related species. These promoters can also be used for blocking the genic expression through anti-sense construction. Under the control of the above mentioned promoters, it is possible to conduct the expression of other genes in filamentary fungi, thereby increasing the production of antibiotics and / or proteins inherent to the same.

The invention discloses a new strain MP688 of Methylovorus sp., of which the preservation number is CGMCC No.4096, the preservation date is August 20th, 2010, and the preservation unit is China General Microbiological Culture Collection Center. The strain MP688 is separated from soil by using a GDH (glutamate dehydrogenase) recombinase method of PQQ (pyrroloquinoline quinone). By using the Methylovorus sp. strain disclosed by the invention, the yield of PQQ can reach 125 mg / L in a conventional culture medium under conventional culture conditions; and the Methylovorus sp. strain can be used for industrial production of PQQ, and has important meaning for promoting the industrialization of PQQ.

The invention discloses a recombinant strain for producing L-2-aminobutyric acid and a preparing method and application thereof. The recombinant strain is a strain obtained in the mode that threonine dehydratase, transaminase and glutamate dehydrogenase are subjected to overexpression at the same time. Due to the recombinant strain for producing the L-2-aminobutyric acid with threonine serving as a substrate, the yield of the L-2-aminobutyric acid and the substrate conversion ratio are remarkably increased, accumulation of by-products is effectively reduced, and the production technology is simplified.

The invention provides a nano antibody of clostridium difficile glutamate dehydrogenase, and an encoding sequence, a screening method and the application thereof and belongs to the technical field ofimmunology. The invention provides an amino sequence of the nano antibody of clostridium difficile glutamate dehydrogenase. By using a phage display technology, a sequence with a constant region specific gene is inserted into a vector of a phage encoding coat protein, after recombination expression, an exogenous gene expression product is fused with the phage encoding coat protein and demonstratedon the surface of phage to form a phage demonstration library, phage monocloning of the nano antibody is expressed through screening, and the nano antibody is prepared through sequencing. Phage-ELLSAidentification shows that the phage that the nano antibody is expressed on the surface can be specifically combined with clostridium difficile glutamate dehydrogenase antigen and has a good developing property, the result shows that the nano antibody has a good combination property with glutamate dehydrogenase, therefore, the nano antibody can be adopted to replace a common antibody applied to aclostridium difficile immunodetection kit.

The present invention provides compounds of Formula (I): wherein variables X, Y, Z and R1 are as described herein. Some of the compounds described herein are glutamate dehydrogenase activators. The invention is also directed to pharmaceutical compositions comprising these compounds, uses of these compounds and compositions in the treatment of metabolic disorders as well as synthesis of the compounds.

The invention discloses a method for synthesizing ursodeoxycholic acid (UDCA) and high-chiral-purity D-amino acid based on an enzyme-method coupling technology. The method comprises the following steps: putting chenodeoxycholic acid and alpha-ketonic acid into a solution system containing 7alpha-HSDH (Homoserine Dehydrogenase), DAADH and NADP (Nicotinamide Adenine Dinucleotide Phosphate) and carrying out enzyme catalysis reaction; separating a reaction solution by adopting an ultra-filtration membrane to obtain a concentrated mixed enzyme solution; regulating the pH (Potential of Hydrogen) ofa dialysis solution and crystallizing; filtering and separating to obtain 7-KLCA wet powder and filtrate; carrying out chromatographic treatment on the filtrate to obtain the D-amino acid; putting the7-KLCA wet powder into a solution system containing glucose, the NADP, the 7alpha-HSDH and GDH (Glutamate Dehydrogenase) and carrying out enzyme catalysis reaction; separating the reaction solution by adopting the ultra-filtration membrane to obtain the concentrated mixed enzyme solution; crystallizing, filtering and separating the dialysis solution, so as to obtain ursodeoxycholic acid. By adopting the method provided by the invention, UDCA and the high-chiral-purity D-amino acid can be obtained at the same time, the enzyme utilization rate is high, synthesis steps are simple and the cost isreduced; meanwhile, a metal reduction reagent and an organic solvent do not need to be added in a reaction process and conditions are mild; the method is environmentally friendly and is suitable forindustrial production.

The invention belongs to the technical field of genetic engineering, and particularly relates to novel high-efficiency gamma-glutamyl methylamine synthetase and a plasmid-free genetic engineering bacterium for L-theanine production and construction and application thereof. The plasmid-free genetic engineering bacterium which performs denovo synthesis on L-theanine efficiently by taking cheap carbon sources such as glucose as a substrate is provided, escherichia coli serves as a host, and gamma-glutamyl methylamine synthase genes gmas-Mu copied three times are integrated on a genome of the escherichia coli; a glutamate dehydrogenase gene Cgl2079 is copied once; a pyruvate carboxylase gene Cgl0689 is copied once; a citrate synthase gene gltA is copied once, and the genetic engineering bacterium is obtained. After metabolic transformation of a system, the engineering bacterium can perform denovo synthesis on the L-theanine by taking the glucose as the raw material, the fermentation yieldand sugar-acid conversion rate are the highest values reported so far, in fermentation of a 5 L fermentor, the maximum production of the L-theanine can reach 60 g / L, and the sugar-acid conversion ratecan reach 40%.

The present invention relates generally to the field of molecular biology and concerns a method for improving various plant growth characteristics by modulating expression in a plant of a nucleic acid encoding a GDH (Glutamate DeHydrogenase) polypeptide. The present invention also concerns plants having modulated expression of a nucleic acid encoding a GDH polypeptide, which plants have improved growth characteristics relative to corresponding wild type plants or other control plants. The invention also provides constructs useful in the methods of the invention. The present invention relates generally to the field of molecular biology and concerns a method for enhancing various economically important yield-related traits in plants. More specifically, the present invention concerns a method for enhancing yield-related traits in plants by modulating expression in a plant of a nucleic acid encoding a FLA-like (Fasciclin-like) polypeptide. The present invention also concerns plants having modulated expression of a nucleic acid encoding a FLA-like polypeptide, which plants have enhanced yield-related traits relative to control plants. The invention also provides constructs comprising FLA-like- encoding nucleic acids, useful in performing the methods of the invention. The present invention relates generally to the field of molecular biology and concerns a method for enhancing yield-related traits in plants by modulating expression in a plant of a nucleic acid encoding a SAUR polypeptide. The present invention also concerns plants having modulated expression of a nucleic acid encoding a SAUR polypeptide, which plants have enhanced yield-related traits relative to corresponding wild type plants or other control plants. The invention also provides constructs useful in the methods of the invention. Furthermore, the present invention also relates to a SAUR-based protein complex. It further relates to the use of the complex to enhance yield-related traits, and to a method for stimulating the complex formation, by overexpressing at least two members of the complex. The present invention relates generally to the field of molecular biology and concerns a method for enhancing yield traits in plants by modulating expression in a plant of a nucleic acid encoding a dehydroascorbate reductase (DHAR) polypeptide. The present invention also concerns plants having modulated expression of a nucleic acid encoding a DHAR polypeptide, which plants have enhancing yield traits relative to corresponding wild type plants or other control plants. The invention also provides constructs useful in the methods of the invention.

The invention discloses an enzyme combination for producing L-phosphinothricin. The enzyme combination comprises glutamate dehydrogenase and a coenzyme regenerating enzyme, wherein the coenzyme regenerating enzyme is alcohol dehydrogenase, formate dehydrogenase and phosphite dehydrogenase. The invention also discloses a production method of L-phosphinothricin, 4-(methylhydroxyphosphinyl)-2-oxobutyric acid is used as a raw material, NH<4><+>, a coenzyme NADP<+> / NADP, and a coenzyme regeneration substrate are added, and then the enzyme combination is used for catalysis, wherein the glutamate dehydrogenase is used to catalyze a reaction of 4-(methylhydroxyphosphinyl)-2-oxobutyric acid to obtain L-phosphinothricin, and the coenzyme regenerating enzyme is used to reduce NADP<+> to NADP. According to the enzyme combination and the production method of L-phosphinothricin provided by the invention, by-products produced are very easy to remove, a post-treatment process of the product is simplified, the total yield of the product is greater than 95%, and the production cost of L-phosphinothricin is reduced, so that the method is a green, environment-friendly, and low-carbon process route, and is suitable for large-scale industrial production applications.

The invention relates to a kit for diagnosing / measuring glycine by utilizing the technologies of the enzymatic doubling amplification method, the enzymic colorimetry and the enzyme linked immunosorbent assay. The invention further relates to a method, a principle and the composition and the components of a reagent for measuring the concentration of the glycine, and belongs to the technical field of medical / food inspection and measurement. The main components of the kit include a buffer solution, coenzyme, a 2-ketoglutaric acid, guanosine monophosphate, glycine aminotransferase, glutamate dehydrogenase, guanosine monophosphate reduced enzyme and a stabilizer. Through mixing a sample and the reagent by a certain volume ratio, a series of enzymatic reactions occur, then the reactant is placed under an ultraviolet / visible light analyzer, and the degree / velocity of the increase in absorbance at 340 nm of the dominant wavelength is detected, thereby measuring the active concentration of the glycine.

The invention discloses a spectrophotometric method for quickly detecting the content of ethyl carbamate, and belongs to the technical field of analytical chemistry and food safety inspection. Ethyl carbamate degrading enzyme and glutamate dehydrogenase construct a double-enzyme coupled system; the ethyl carbamate degrading enzyme hydrolyzes the ethyl carbamate to generate ethyl alcohol, water and ammonia, the ammonia reacts with a cosubstrate alpha-ketoglutarate under the catalysis of the glutamate dehydrogenase to generate glutamic acid, and reduced coenzyme namely NADH (Nicotinamide Adenine Dinucleotide Hydrogen) is oxidized concomitantly, so that the system changes the content of the ethyl carbamate into the content of the NADH, and the content of the ethyl carbamate in a liquid-state system can be detected by using the change of the light absorption value of the NADH at 340nm. By virtue of the method, the ethyl carbamate in a solution can be quickly detected, the ethyl carbamate in a yellow wine system can be simulated, the detection limit is as low as 0.1mu mol. L<-1>, and an effective way is provided for the detection of the ethyl carbamate in fermented food and beverages.

The reagent kit for enzyme detection of blood ammonia consists of tromethamine in 50-150 mmol, Tween-20 in 0.1-2 ml, sodium azide om 0.5-2 g, lactose in 5-50 g, glutamate dehydrogenase in 500-1500 u, alpha-ketoglutaric acid in 2-20 mmol, sodium acetonate in 1-10 mmol, and reducing nicotin-amide-adenine dinuclectide phosphate in 0.1-0.5 mmol. After regulating pH to optimal value of 8.0, the components are dissolved, packed and freeze dried and may be cold stored for two years. After being re-dissolved, the components are stabilized at room temperature for 1 week and cold stored to stabilize for 1 month. The reagent kit has powerful interference resistance, medium hemolysis and chylemia, blood sugar below 20 mmol / L, bilirubin below 0.1 mmol / L, enzyme activity loss less than 5 %, MADPH loss less than 10 %, linearity reaching 0.2 mmol / L, CV inside batch of 3.8 % and CV between batches of 5.1 %, and recovering rate of 96.1 %.

The invention relates to the technical field of urea detection, in particular to a preparation method of a urea determination reagent ball, the reagent ball and a detection chip. The embodiment of theinvention provides a preparation method of a urea determination reagent ball. The method comprises the following steps of mixing a certain dosage of buffer solution, disodium ethylene diamine tetraacetate, alpha-ketoglutarate, glutamate dehydrogenase, urease, reduced nicotinamide adenine dinucleotide and excipient with water to form a mixed solution, dropwise adding the mixed solution into liquidnitrogen to enable liquid drops of the mixed solution to form ice balls, and freeze-drying the ice balls to obtain spherical urea determination reagent balls. The urea determination reagent ball prepared by the method has good thermal stability, can be stored for 8 days at a high temperature of 37 DEG C, is not easy to deteriorate in the storage process, has a wide effective test range on urea inblood, and can test the highest concentration of blood urea as high as 35mmol / L.

Provided herein are SIRT4 compositions and methods of use thereof. The invention provides functional information for use in the identification and design of compounds that modulate SIRT4 enzyme activity (e.g., inhibition of fatty acid oxidation, ADP ribosylation, and / or downregulation of glutamate dehydrogenase), and to the compounds identified by such methods and the research, diagnostic and therapeutic uses of such compounds.

The present invention relates to glutamate dehydrogenase mutants and their application in preparation of L-phosphinothricin. The amino acid sequences of the glutamate dehydrogenase mutants are as shown in SEQ ID NO. 1˜9, 11, 13, 15, 17˜19 and 22. By means of molecular engineering, mutating the specific alanine in glutamate dehydrogenase substrate-binding pocket into glycine and / or mutating the specific valine in glutamate dehydrogenase substrate-binding pocket into alanine, the present invention has obtained NADPH-specific glutamate dehydrogenase mutants with high enzyme activity in catalyzing the substrate 2-oxo-4-[(hydroxy)(methyl)phosphinoyl]butyric acid or its salt for L-phosphinothricin preparation or NADH-specific glutamate dehydrogenase mutants with catalytic activity toward PPO; this has significantly improved substrate conversion, and increased the product concentration of the L-phosphinothricin preparation process.

The invention relates to a 5'-nucleotidase diagnosis reagent box of Enzymatic Recycling Method, and the invention also relates to method principle for detecting the solution of 5'-nucleotidase, constitute and component of reagent, which belongs to the technical field of medical checking measurements. The reagent box in the invention can be dry powder state, and used after dissolution; it also can be formulated to be liquid agent for direct usage. The component of reagent box mainly contains: buffering liquid, alpha- ketoglutaric acid, reduction type coenzyme, Adenosine Deiminase EC 3.5.4.4, glutamate dehydrogenase EC 1.4.1.2, EC 1.4.1.3, EC 1.4.1.4, Glutamate oxidase EC 1.4.3.7, EC 1.4.3.11, peroxidase EC 1.11.1.7, reduction type chromogen assembly, stabilizer and anti-interference agent; and the component can be mixed to form single-reagent reagent box, two-reagent reagent box, and three-reagent reagent box; by series of enzymatic reaction, the colorless reduction type chromogen assembly is oxygenated to form color dye, and the content of dye can be measured by visible light analyzer at wavelength of 400-700nm to reflect the concentration of 5'-nucleotidase directly. Comparing with present technique, the invention can be spread easily, and because the produced dye has higher molar extinction coefficient, the sensitivity is high, and the precision is well.

The invention discloses a kit of single reagent used for diagnosing monoamine oxidase (MAO) in serum. MAO hydrolyzed benzylamine, butyl amine, amyl amine, Beta-phenylethyl amine and other amine compounds are utilized to produce oxygen; the oxygen reacts with glutamate dehydrogenase in a coupling way; oxidized coenzyme is formed by the reaction of reduced coenzyme; and the activity of sample MAO formed by quantitative reaction is calculated through measuring the descending speed of the absorbance of light with a wavelength of 340 nm; in addition, enzyme and substrate enzyme which can slowly generate reduced nicotinoyl coenzyme are added in the reaction process, so that an enzyme-substrate enzyme-nicotinoyl coenzyme slow reaction system is formed in single reagent and the nicotinoyl coenzyme can be compensated slowly and circularly and further the single reagent can be stabilized when the concentration of the single reagent achieves a certain balance. The kit is convenient for use and simple is structure, can be used on a common ultraviolet / visible light analyzer or a semi-automatic / full-automatic biochemical analyzer for rapid measurement without using a special or additional apparatus and has low cost.

The invention relates to a homocysteine concentration measuring method. The method includes: oxidizing homocysteine to generate alpha-butanone acid, ammonia and hydrogen sulfide; using ammonia to convert NADH into NAD+ under action of glutamate dehydrogenase; quantifying by measuring light absorbance of NADH at a position of 340nm. The homocysteine diagnosis kit comprises a reagent I and a reagent II, the reagent I contains reduced coenzyme I, glutamate dehydrogenase, tri(2-carboxyethyl) phosphine hydrochloride, alpha-ketoglutaric acid, surfactant, buffer solution and stabilizer, and the reagent II contains HCYase, phosphopyridoxal, buffer solution and stabilizer. The homocysteine diagnosis kit and the homocysteine concentration measuring method have the advantages that the kit for detecting homocysteine in human serum through two liquid reagents is built, and an additional fluorescence detector is not needed, so that convenience is brought to detection of plenty of samples; the method is free of interference by pyruvic acid, methionine and cysteine in the samples and lower in cost.

The invention discloses a method for simultaneous determination of double items of urea nitrogen and creatinine in serum, and belongs to the method for testing a material through testing color changes of reaction results by using visible light; the technical scheme comprises that a reagent II only comprises effective components of creatinine amidohydrolase and creatine amidinohydrolase; a reagent I contains effective components of urease, glutamate dehydrogenase, alpha-ketoglutarate and NADH. The determination method comprises the steps: firstly, carrying out 37 DEG C warm bath of serum with the reagent I for 3-5 minutes; carrying out a reaction of urea in the serum with the reagent I to generate NAD+; adding the reagent II, carrying out 37 DEG C warm bath for 4-7 minutes, hydrolyzing creatinine with the creatinine amidohydrolase to generate creatine; making the creatine generate urea under the action of the creatine amidinohydrolase, and making the urea and the reagent I generate NAD+ under the action of urease; at the wavelength of 340 nm, comparing the reaction speed with that of a standard treated by the same way, determining the change of the first-step reaction NADH, namely the content of urea nitrogen in the serum, and determining the change of the second-step reaction NADH, namely the content of the creatinine in the serum.

The invention belongs to the technical field of genetic engineering, and particularly relates to novel high-efficiency gamma-glutamyl methylamine synthetase and a plasmid-free genetic engineering bacterium for L-theanine production and construction and application thereof. The plasmid-free genetic engineering bacterium which performs denovo synthesis on L-theanine efficiently by taking cheap carbon sources such as glucose as a substrate is provided, escherichia coli serves as a host, and gamma-glutamyl methylamine synthase genes gmas-Mu copied three times are integrated on a genome of the escherichia coli; a glutamate dehydrogenase gene Cgl2079 is copied once; a pyruvate carboxylase gene Cgl0689 is copied once; a citrate synthase gene gltA is copied once, and the genetic engineering bacterium is obtained. After metabolic transformation of a system, the engineering bacterium can perform denovo synthesis on the L-theanine by taking the glucose as the raw material, the fermentation yieldand sugar-acid conversion rate are the highest values reported so far, in fermentation of a 5 L fermentor, the maximum production of the L-theanine can reach 60 g / L, and the sugar-acid conversion ratecan reach 40%.