553 results about "Methionine biosynthesis" patented technology

The invention relates to the technical field of gene engineering and enzyme engineering, in particular to an esterase mutant for degrading ethyl carbamate and application of the esterase mutant, the esterase mutant has an amino acid sequence as shown in SEQ ID NO.1 which is subjected to site mutation, the site mutation is any one or more site combined mutation of V129S, V161L or I229M, and the amino acid sequence of the esterase mutant is shown in SEQ ID NO.1. The V129S site mutation is that valine at the 129 site is mutated into serine, the V161L site mutation is that valine at the 161 site is mutated into leucine, and the I229M site mutation is that isoleucine at the 229 site is mutated into methionine. Mutation is carried out through a site-directed mutagenesis method, so that the amino acid sequence of the esterase mutant V129S / I229M is changed, the autoplasmic structure and function of eggs are changed, the esterase mutant V129S / I229M with the ethyl carbamate hydrolysis rate increased to 6.55 times in an acid environment is finally obtained, and the esterase mutant V129S / I229M has high industrial application value.

The invention discloses a method for regulating the transport activity of a strain to 1-aminocyclopropane-1-carboxylic acid, and relates to the technical field of bioengineering. The method for regulating and controlling the transport activity of the strain to 1-aminocyclopropane-1-carboxylic acid and / or methionine analogues and the tolerance of the strain to the 1-aminocyclopropane-1-carboxylic acid and / or methionine analogues, disclosed by the invention, comprises the step of transferring a LeuE gene into escherichia coli to obtain an escherichia coli recombinant strain with corresponding functions. The invention discloses the application of the LeuE protein and the LeuE gene in regulating and controlling the transport activity of escherichia coli to the 1-aminocyclopropane-1-carboxylic acid and / or methionine analogue and the tolerance of escherichia coli to the 1-aminocyclopropane-1-carboxylic acid and / or methionine analogue for the first time. The invention discloses that LeuE is an optimal candidate gene for constructing ACC synthetic bacteria for the first time, and the substrate specific transport of the LeuE meets the aim of enhancing the ACC tolerance of cells without influencing precursor supply.

There is provided a fluorinase variant thereof having at least 70% sequence identity to a sequence MSDLGX6TDDSVAQCKGLMLSICPX24VX26IX28DX30CHX33MTPX37DVVEGARYIVDLPR X52FPEGTVFATTTYPATGTX70X71RSVAX76RX78KX80AALGGARGQX90AGSGX95GX97E RAEGX103YIYIAPNNGLLTX116VIEEHGYX124EAYEVSX131TX133VIPX137X138PEPTFYSR EMVAIPSAHLAAGFPLX163X164VGRX168LX170DX172EIVRFEX179X180KX182X183X184VX186G X188X189LX191GX193X194X195X196X197DHPFGNX204WTNX208HRTDLEKAGIX219YX221TX223X 224KX226VX228DGVLX233FX235LPLX239PTFADAX246X247X248GX250PVX253YX255NSRGYLX2 62X263ARNAAX269LAYPYNLX277AGX280SVX283VTX286A (SEQ ID NO: 1), wherein X is a natural amino acid, and wherein the variant comprises one or more mutations at a site selected from the group consisting of an ion-egress site, a S-Adenosyl-L-Methionine (SAM) binding site, an ion-binding site (IBS), and a conserved site. Also disclosed are polynucleotides encoding the variants, vectors comprising the polynucleotides encoding the variants, and host cells comprising the vectors thereof. Also disclosed are Methods for producing the variants, methods of catalyzing the fluorination of a compound, uses of the fluorinase variants, and methods of treatment using the fluorinase variants thereof.

The invention relates to laccase as well as a mutant and application thereof, and belongs to the technical field of biology. The amino acid sequence of the laccase PnLac1 is as shown in SEQ ID NO. 2, and the nucleotide sequence of the laccase PnLac1 is as shown in SEQ ID NO. 1. The mutant is characterized in that aspartic acid at the 166th position of laccase PnLac1 is subjected to site-specific mutagenesis, histidine at the 348th position of laccase PnLac1 is subjected to site-specific mutagenesis, methionine at the 403th position of laccase PnLac1 is subjected to site-specific mutagenesis, or leucine at the 467th position of laccase PnLac1 is subjected to site-specific mutagenesis, amino acid sequences are shown as SEQ ID NO.4, SEQ ID NO.6, SEQ ID NO.8 and SEQ ID NO.10, and nucleotide sequences are shown as SEQ ID NO.3, SEQ ID NO.5, SEQ ID NO.7 and SEQ ID NO.9. The decoloring efficiency of the laccase PnLac1 on crystal violet reaches 5h, and the degradation rate reaches 75%. When the ABTS is used as a substrate, the enzyme activities of the laccase mutants H348F and L467M are respectively improved by 1.89 times and 1.65 times, and the ABTS has the potential of degrading stubborn substances; when guaiacol is used as a substrate, the enzyme activities of the laccase mutants D166A and M403F are respectively improved by 2.07 times and 3.72 times, and the guaiacol has a relatively high application prospect in the field of lignin.

The invention discloses a high-activity TET dioxygenase mutant as well as a construction method and application thereof. The TET dioxygenase mutant is obtained from an amino acid sequence of wild type TET dioxygenase as shown in SEQ ID NO.1 according to any one of the following mutation modes: a, the 150th proline is mutated into alanine; and b, proline at the 150th site is mutated into alanine, and isoleucine at the 235th site is mutated into methionine. The TET dioxygenase mutant provided by the invention can be stabilized in an escherichia coli system, the purification effect is good, the preparation difficulty is reduced, and the activity is remarkably improved compared with that of a wild type. The methylation gene transformation effect is far better than that of a traditional bisulfite transformation method, and the method has a good application prospect.

The invention discloses a method for efficiently producing ergothioneine by metabolic engineering modified escherichia coli and application, and belongs to the technical field of biology. By adopting the recombinant escherichia coli EGT-1-B * provided by the invention, glucose can be converted into ergothioneine; therefore, the raw materials are cheap and easy to obtain, additives and heavy metals which are harmful to human health are avoided, a good foundation is laid for later product purification, and the requirements of commercial application can be met. Furthermore, genes related to metabolism of histidine, methionine, cysteine and S-adenosylmethionine are further overexpressed in the recombinant escherichia coli EGT-1-B *, so that the content of precursor amino acid synthesized by the ergothioneine is increased, and meanwhile, after the gene yqaB is knocked out, the yield of the ergothioneine is further increased; the utilization rate of glucose to ergothioneine can be further improved, and the yield of ergothioneine can reach 140.29 mg / L.

The invention discloses a gelator and a preparation method and application thereof, the structural formula of the gelator is # imgabs0 #, R1 is a side chain group connected to an amino acid central carbon atom except an amino group, a carboxyl group and a hydrogen atom; the amino acid is selected from one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrole lysine; the amino acid is selected from one of glycine, alanine, valine, leucine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, lysine, arginine, histidine, selenocysteine and pyrrole lysine; r2 is alkyl with the carbon atom number of 16 to 19; and R3 is 9-fluorenyl methoxy carbonyl group or t-butyloxycarbonyl group. The gelator has a hydrophobic long alkyl tail chain, can spontaneously gather and assemble into a three-dimensional network structure through hydrogen bonds, pi-pi interaction and hydrophobic force, and fixes an oil phase in an oil solvent or an oil-water mixture in an effective manner to form high-strength gel.

The invention discloses a high-stability carbonyl reductase mutant and application of the high-stability carbonyl reductase mutant in chiral alcohol synthesis. An amino acid sequence as shown in SEQ ID NO.2 is mutated as follows: 20th leucine is replaced by any one of lysine, threonine, aspartic acid or isoleucine, and / or 55th leucine is replaced by any one of methionine, serine, lysine or isoleucine, and / or 55th leucine is replaced by any one of methionine, serine, lysine or isoleucine. Compared with a wild type enzyme, the stability of the obtained mutant is remarkably improved, particularly, single-point mutants Mut-L20I and Mut-L55I and a combined mutant Mut-L20I-L55I show excellent relative enzyme activity, thermal stability and substrate tolerance. The mutant has high catalytic activity and stability to various chiral alcohols, has the advantages of high catalytic efficiency, high thermal stability, strong substrate tolerance, easiness in fermentation production and the like, and is suitable for industrial application of enzymatic synthesis of chiral alcohols.

The invention relates to the field of plant molecular biology and forest genetic engineering, and particularly provides a PagRAP2.3 protein point mutant and application thereof in drought resistance of poplar. The mutant PagRAP2.3 MA is obtained by mutating methionine at the first site and cysteine at the second site of a wild type PagRAP2.3 protein into methionine and alanine. The invention further discloses a preparation method of the mutant PagRAP2.3. An expression vector containing the PagRAP2.3 MA gene is constructed, poplar 84K is transformed through an agrobacterium-mediated method, and a transgenic line with stable expression is obtained. Functional verification results show that overexpression of PagRAP2.3 MA can significantly increase the plant height of the poplar and promote plant growth, but the sensitivity to moisture is enhanced under drought stress. The mutant can be used for regulating and controlling the growth and development of forest trees and evaluating the drought resistance, and has a forestry breeding application prospect.

A pharmaceutical composition comprising a protein arginine methyltransferase 5 (PRMT5) inhibitor and a methionine adenosyltransferase IIα (MAT2A) inhibitor. The pharmaceutical composition can be used for treating various cancers, comprising solid tumors. The combined product can be used for treating any number of diseases associated with PRMT5 and / or MAT2A.

The invention provides a penicillin G acylase AxPGA mutant, an expression plasmid, a genetically engineered bacterium and application, and belongs to the technical field of biocatalysts. The mutant is obtained by mutation of any one or more of the following sites of an amino acid sequence as shown in SEQ ID NO: 1: (1) methionine at the 103rd site is substituted by cysteine, (2) tyrosine at the 424th site is substituted by phenylalanine, (3) tyrosine at the 442nd site is substituted by phenylalanine, and (4) tyrosine at the 451st site is substituted by alanine. The obtained penicillin G acylase AxPGA mutant is relatively high in enzyme activity and can be applied to high-conversion-rate and high-yield synthesis of beta-lactam antibiotics such as benicillin and amoxicillin.

The present application relates to a pyridoxal kinase mutant, a recombinant expression vector and a microbial cell and their applications, and belongs to the technical field of biological catalysis. In order to solve the problem of low product concentration in existing enzyme catalysis, a pyridoxal kinase mutant is provided, the amino acid sequence is selected from the amino acid sequence shown in SEQ ID NO. 1, the lysine at position 229 is mutated to alanine, phenylalanine, methionine, arginine, threonine, histidine, serine, tyrosine, valine, leucine, isoleucine, proline, asparagine, aspartic acid or glutamic acid; the pyridoxal kinase mutant is used for catalyzing pyridoxal to synthesize pyridoxal phosphate, and a recombinant expression vector and a microbial cell can be further formed. The present application has good enzyme activity, high product conversion rate, high concentration of pyridoxal phosphate obtained, and the concentration of the product catalyzed by the wild-type pyridoxal kinase to phosphorylate pyridoxal is obviously improved.

The mixture as the micronutrient composition is a combination of alpha-ketoglutaric acid, nicotinamide or nicotinic acid, L-proline, L-glutamine, L-citrulline, sodium pyruvate, pantothenic acid, L-cysteine or N-acetylcysteine, magnesium malate, magnesium citrate, and methionine. The mixture is effective for the treatment of diseases due to oxidative stress. More specifically, the mixtures and cores as micronutrient compositions are effective in reversing saccharification in diabetes mellitus.

The invention belongs to the technical field of biological detection, and particularly relates to a method for synchronously and quantitatively detecting various folic acid metabolism related substances in trace plasma or serum, which comprises the following steps of: detecting a pretreated trace plasma or serum sample by adopting a liquid chromatography-tandem mass spectrometry method; the following nine folic acid metabolism related substances are synchronously and quantitatively detected: 5-formyl tetrahydrofolic acid, folic acid, 5-methyl tetrahydrofolic acid, S-adenosine-L-methionine, S-adenosine-L-homocysteine, vitamin B12, pyridoxamine, pyridoxine and pyridoxal. The invention further relates to application of the detection method in related detection of child neurodevelopment. According to the detection method, only trace plasma or serum is used, methotrexate is used for replacing an expensive isotope internal standard for more economical detection, and nine folate metabolism related substances can be accurately quantified at the same time. Therefore, the detection method disclosed by the invention has important clinical significance and wide market application prospect.

The invention relates to a blood protein peptide for promoting hair follicle reconstruction and application thereof, and belongs to the technical field of bioactive peptides. The blood protein peptide disclosed by the invention is selected from one or more of an MLL peptide fragment and a WDL peptide fragment; the amino acid sequence of the MLL peptide fragment is as follows: methionine-leucine-leucine; the amino acid sequence of the WDL peptide fragment is as follows: tryptophan-aspartic acid-leucine. The invention also provides a preparation method of the blood protein peptide and application of the blood protein peptide in hair follicle reconstruction. The blood protein peptide prepared by the technical scheme of the invention can obviously improve local blood supply around hair follicles, and has a wide application prospect in the field of treatment of alopecia.

The invention discloses a chitosanase mutant which is derived from bacillus subtilis and has the capacity of hydrolyzing chitosan to produce chitosan disaccharide per unit and belongs to a GH46 family, and application of the chitosanase mutant in hydrolyzing chitosan to produce chitosan oligosaccharide. Compared with wild type chitosanase capable of producing chitodisaccharide and chitotriose, the chitosanase mutant has the advantage that the chitodisaccharide can be produced per unit when the chitodisaccharide is hydrolyzed by the chitosanase mutant. The invention provides eight kinds of chitosanase mutants, and the mutants are obtained by carrying out site-specific mutagenesis on 21st-site glycine on the basis of wild type chitosanase and respectively mutating the 21st-site glycine into lysine, arginine, leucine, histidine, methionine, tyrosine, proline and glutamine. The mutant can hydrolyze chitosan under mild conditions to produce chitosan oligosaccharide with single polymerization degree, and can greatly relieve the difficulty in separation and purification in chitosan oligosaccharide production.

The invention provides a T7-RNA polymerase mutant capable of reducing generation of dsRNA and application of the T7-RNA polymerase mutant, tryptophan at the 328th site from the N terminal of an amino acid sequence of wild type T7-RNA polymerase is substituted by methionine, phenylalanine, asparagine, alanine or lysine, and a by-product dsRNA generated in an in-vitro transcription process can be reduced. Through computer simulation, a large amount of screening work is reduced, the enzyme evolution speed is increased, and the cost and time of enzyme modification are greatly reduced; the T7-RNA polymerase mutant maintains efficient transcription, reduces the complexity of later purification work, reduces the purification cost of RNA production, can quickly prepare RNA drugs meeting the use requirements, and provides an efficient tool enzyme for large-scale production of the RNA drugs.

The invention discloses recombinant escherichia coli and a method for producing L-methionine by using the recombinant escherichia coli. L-methionine is produced through fermentation culture of recombinant escherichia coli, sulfur source optimization is carried out on a sulfur source culture medium used during fermentation culture, the sulfur source utilization efficiency is improved, and the yield of L-methionine is increased; in the optimization process, generation of hydrogen sulfide in a culture medium is detected by lead acetate test paper, so that metZ genes for expressing and coding O-succinyl homoserine sulfhydrylase are introduced into plasmid pAm to obtain plasmid pAmZ, and the plasmid pAmZ is introduced into strains M2 / pAm and M2-HPBC / pAm to obtain recombinant escherichia coli M2 / pAmZ and M2-HPBC / pAmZ, so that the toxic action of hydrogen sulfide on cells is reduced, and the yield of hydrogen sulfide is increased. The yield of the L-methionine can be increased; according to the present invention, the recombinant escherichia coli M2 / pAmZK and the recombinant escherichia coli M2-HPBC / pAmZK are obtained by further introducing the ppnk gene expressing and coding NAD + kinase into the plasmid pAmZ, and introducing the ppnk gene into the bacterial strains M2 / pAmZ and M2-HPBC / pAmZ to obtain the recombinant escherichia coli M2 / pAmZK and M2-HPBC / pAmZK, such that the intracellular NADPH level is improved, and the L-methionine yield is further improved;

The invention discloses a ternary synergetic reinforced carbon quantum dot as well as a preparation method and application thereof. The preparation method comprises the following step: carrying out hydrothermal reaction on a mixed reaction system at least containing citric acid and / or a citric acid derivative, methionine and / or a methionine derivative and a copper source at 180-300 DEG C to prepare the ternary synergistic reinforced carbon quantum dots. The ternary synergetic reinforced carbon quantum dots have excellent water solubility and antibacterial performance, nitrogen and sulfur atoms enter the carbon quantum dots to form active sites on the surfaces of the carbon quantum dots and are subjected to chemical coordination with metal copper ions, and the synergetic antibacterial performance of the carbon quantum dots and the metal copper ions is fully exerted; meanwhile, the good water solubility can effectively improve the dispersity of the bacteriostatic agent in a water environment.

The invention belongs to the technical field of biology, and particularly relates to a CHO cell suspension culture medium as well as a preparation method and application thereof. The culture medium comprises amino acids, vitamins, inorganic salts, trace elements, carbohydrates and other molecular compounds; the amino acids comprise glycine, L-alanine, L-arginine, L-asparagine, L-aspartic acid, L-cysteine, L-cystine, L-glutamic acid, L-histidine, L-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-proline, L-serine, L-threonine, L-tryptophan, L-tyrosine and L-valine. The culture medium provided by the invention can meet the high-density suspension culture of various CHO cells, can improve the production efficiency and reduce the production cost, and has wide application prospects and values. The culture medium provided by the invention overcomes the defects of the existing culture medium with determined chemical components, and provides more choices for the culture medium with determined chemical components in China.

Provided are a microorganism in which activity of an SIRT-type deacetylase protein is weakened; a method for producing O-acetyl homoserine and L-methionine using the same; a composition for producing O-acetyl homoserine, the composition including the microorganism; and use of the microorganism for producing O-acetyl homoserine or L-methionine.

The invention discloses a pediatric compound amino acid injection and a preparation method thereof, and relates to the technical field of medicines. The invention relates to a preparation method of a pediatric compound amino acid injection. The preparation method comprises the following steps: carrying out vacuumizing and nitrogen charging treatment on a pipeline and a preparation tank for preparation; the preparation method comprises the following steps: adding low-oxygen injection water into a preparation tank, heating, continuously charging nitrogen, adding isoleucine, leucine, lysine acetate, methionine, phenylalanine, threonine, valine, histidine, tyrosine, acetyl tyrosine, alanine, arginine, proline, serine, glycine, aspartic acid and taurine, and stirring for dissolving; cooling the preparation tank, adding glacial acetic acid, then adding tryptophan, glutamic acid and cysteine hydrochloride, stirring and dissolving, adding the residual water for injection, and then adding glacial acetic acid to adjust the pH value to obtain a liquid medicine; carrying out intermediate determination on the liquid medicine, filtering, filling, and sealing; and carrying out hot-pressing sterilization on the sealed liquid medicine, and loading the sterilized liquid medicine and an oxygen absorbent into a barrier bag for vacuum packaging. The safety of the compound amino acid can be improved.

The invention relates to a pyridoxal kinase mutant, a recombinant expression vector, a microbial cell and application thereof, and belongs to the technical field of biological catalysis. In order to solve the problem of low concentration of the existing enzyme catalysis product, the invention provides the pyridoxal kinase mutant. The amino acid sequence is selected from lysine at the 229 site of the amino acid sequence as shown in SEQ ID NO.1, and the lysine at the 229 site of the amino acid sequence as shown in SEQ ID NO.1 is mutated into alanine, phenylalanine, methionine, arginine, threonine, histidine, serine, tyrosine, valine, leucine, isoleucine, proline, asparagine, asparaginic acid or glutamic acid; the pyridoxal kinase mutant is used for catalyzing pyridoxal to synthesize pyridoxal phosphate, and recombinant expression vectors, microbial cells and the like can be further formed. The pyridoxal phosphate has good enzyme activity and high product conversion rate, the concentration of the obtained pyridoxal phosphate is high, and the concentration of a product obtained by catalyzing phosphorylation of pyridoxal through the pyridoxal phosphate kinase is obviously improved compared with that of a product obtained by catalyzing phosphorylation of pyridoxal through wild type pyridoxal kinase.

The invention discloses a method for improving the fermentation performance of clostridium aerovorans and application of the clostridium aerovorans, and according to the method, an effective amount of methionine or a derivative thereof is added into a fermentation culture medium of the clostridium aerovorans to completely replace expensive complex organic nitrogen sources such as yeast extracts. The method successfully solves the three technical bottlenecks of slow biomass accumulation, low ethanol yield and dependence on expensive nitrogen sources in the fermentation process of the clostridium aerovorans by utilizing synthesis gas or CO2 / H2 mixed gas. Experiments prove that methionine or a derivative thereof can synergistically promote growth metabolism of thalli and a synthesis path of a product, so that the gas conversion efficiency of a carbon source is remarkably improved and metabolism is guided to flow to ethanol synthesis while the growth rate and the final biomass of the thalli are improved, and thus the production capacity of alcohols is synchronously enhanced. The method is simple in process and remarkable in effect, and an efficient and economical new strategy is provided for reducing the production cost of biofuel and promoting industrial application of a synthesis gas biorefinery technology.

The invention provides an application of synbiotics in preparation of a composition for improving glucagon-like peptide-1 (GLP-1). The composition comprises litchi polyphenol, probiotics and methionine. The probiotics comprise bifidobacterium animalis BCRC910645, bifidobacterium longum BCRC910812, or a combination of the bifidobacterium animalis BCRC910645 and the bifidobacterium longum BCRC910812, so that the content of the glucagon-like peptide-1 is increased.

The invention relates to the technical field of biological catalysis, in particular to an immobilized formate dehydrogenase mutant and application of the immobilized formate dehydrogenase mutant in electroenzymatic catalysis of CO2. The formate dehydrogenase mutant comprises the following mutations on the basis of clostridium wild formate dehydrogenase: methionine at the 269th site is mutated into isoleucine, serine at the 285th site is mutated into alanine, and serine at the 637th site is mutated into alanine; the NCBI (National Center of Biotechnology Information) accession number of the wild formate dehydrogenase of the clostridium is WP082085143.1. The immobilized formate dehydrogenase mutant provided by the invention has better catalytic activity, temperature, pH stability and storage stability, and can be repeatedly utilized. The immobilized formate dehydrogenase mutant or an electrode material prepared from the immobilized formate dehydrogenase mutant can efficiently catalyze CO2 to be converted into formic acid or formate, which has important significance in the field of renewable energy utilization.

The invention provides a recombinant O-succinyl-L-homoserine mercaptotransferase mutant, a coding gene thereof, a recombinant vector containing the coding gene of the mutant, a recombinant genetically engineered bacterium obtained by converting the recombinant vector, and application of the recombinant O-succinyl-L-homoserine mercaptotransferase mutant in preparation of L-methionine. The novel recombinant O-succinyl-L-homoserine mercaptotransferase mutant with high activity and high selectivity is used as a catalyst to be applied to catalysis of O-succinyl-L-homoserine for synthesis and preparation of L-methionine, a catalytic reaction system is optimized, the feed ratio and reaction conditions in the reaction are finely regulated and controlled, and the yield of L-methionine is increased. The recombinant O-succinyl-L-homoserine mercaptotransferase mutant has high enzyme activity under the optimal reaction condition, the catalytic efficiency is further improved, the purposes of reducing cost and improving efficiency are achieved, and the method has important significance in promoting industrial application of biological catalysis preparation of L-methionine.

The invention belongs to the technical field of bioengineering, and relates to an ArsL mutant and an application of the ArsL mutant in synthesis of Arsinothricin. The ArsL mutant is a mutant obtained by mutating the 428th cysteine C of the amino acid sequence of wild AST synthetase ArsL into alanine A, and the amino acid sequence of the ArsL mutant is as shown in SEQ ID No.2. The invention also discloses a preparation method of the ArsL mutant. The invention also further provides an application of the ArsL mutant in catalysis of sodium methyl arsenate and S-adenosylmethionine to synthesize Arsinothricin. The invention further provides an application of the ArsL mutant in catalysis of sodium methyl arsenate and S-adenosylmethionine to synthesize Arsinothricin. The ArsL mutant disclosed by the invention has higher catalytic activity and thermal stability, the process of converting high-concentration MMA into AST is realized by utilizing the ArsL mutant, and the catalytic activity of the ArsLC428A mutant is obviously improved compared with that of wild type AST synthetase. In addition, compared with an organic synthesis path, a semi-organic enzyme synthesis path and a natural biological synthesis path, the yield of the synthesis path provided by the invention is obviously improved, and the ArsL mutant can be used as a potential industrial application enzyme and has a wide application prospect.

The invention belongs to the technical field of biology, and particularly relates to a 3D protein mutated O-type foot-and-mouth disease recombinant virus strain as well as construction and application thereof. The 403th methionine of the O-type foot and mouth disease virus 3D protein is mutated into alanine, the recombinant virus strain rFMDV-M403A with the mutated O-type foot and mouth disease virus 3D protein is successfully constructed and saved by using a reverse genetic technology, and amino acid of the recombinant virus strain can be stably mutated in a passage process; the growth speed of the mutant strain is slower than that of a wild strain, and the virus titer is remarkably reduced; in an individual experiment, neonatal mouse infection shows that the mutant strain can improve the survival rate of neonatal mice, and the virus load and tissue lesion in the liver are remarkably reduced. The attenuated foot-and-mouth disease recombinant virus strain provided by the invention provides important significance for deep understanding of a foot-and-mouth disease virus pathogenic mechanism and a prevention and control strategy, and also provides an important theoretical basis for further development of a foot-and-mouth disease genetic engineering vaccine.

A bifidobacterium enrichment agent and a use thereof in high-density fermentation. The components of the bifidobacterium enrichment agent include potassium carbonate, arginine, methionine, serine, vitamin C, vitamin B1, vitamin B5, thymine, and calcium pantothenate. The bifidobacterium enrichment agent is added to a basal medium for high-density fermentation, so that the proliferation performance of bifidobacteria can be significantly improved, and the production efficiency can be improved, providing the possibility of preparing a highly active bifidobacterium fermentation liquor, and also providing support for the subsequent preparation and application of bacterial agents.