L-glutamate Oxidase Research Articles

PACKTEST for L-Glutamate Quantification: Development of On-site and High-throughput Analytical Kits Using L-Glutamate Oxidase Mutant

PACKTEST for L-Glutamate Quantification: Development of On-site and High-throughput Analytical Kits Using L-Glutamate Oxidase Mutant

Indirect Voltammetry Detection of Non-Electroactive Neurotransmitters Using Glassy Carbon Microelectrodes: The Case of Glutamate

Glassy carbon (GC) microelectrodes have been successfully used for the detection of electroactive neurotransmitters such as dopamine and serotonin through voltammetry. However, non-electroactive neurotransmitters such as glutamate, lactate, and gamma-aminobutyric acid (GABA) are inherently unsuitable for detection through voltammetry techniques without functionalizing the surface of the microelectrodes. To this end, we present here the immobilization of the L-glutamate oxidase (GluOx) enzyme on the surface of GC microelectrodes to enable the catalysis of a chemical reaction between L-glutamate, oxygen, and water to produce H2O2, an electroactive byproduct that is readily detectable through voltammetry. This immobilization of GluOx on the surface of bare GC microelectrodes and the subsequent catalytic reduction in H2O2 through fast-scan cyclic voltammetry (FSCV) helped demonstrate the indirect in vitro detection of glutamate, a non-electroactive molecule, at concentrations as low as 10 nM. The functionalized microelectrodes formed part of a four-channel array of microelectrodes (30 μm × 60 μm) on a 1.6 cm long neural probe that was supported on a flexible polymer, with potential for in vivo applications. The types and strengths of the bond between the GC microelectrode surface and its functional groups, on one hand, and glutamate and the immobilized functionalization matrix, on the other hand, were investigated through molecular dynamic (MD) modeling and Fourier transform infrared spectroscopy (FTIR). Both MD modeling and FTIR demonstrated the presence of several covalent bonds in the form of C-O (carbon–oxygen polar covalent bond), C=O (carbonyl), C-H (alkenyl), N-H (hydrogen bond), C-N (carbon–nitrogen single bond), and C≡N (triple carbon–nitrogen bond). Further, penetration tests on an agarose hydrogel model confirmed that the probes are mechanically robust, with their penetrating forces being much lower than the fracture force of the probe material.

A Study on the Efficient Preparation of α-Ketoglutarate with L-Glutamate Oxidase.

Alpha-ketoglutaric acid (α-KG), as an intermediate product of the tricarboxylic acid cycle, plays a crucial role in peptide and amino acid synthesis. In order to reduce costs and improve efficiency in the oxidative production of α-ketoglutaric acid, this study successfully synthesized and expressed L-glutamate oxidase (LGOXStr) from Streptomyces viridosporus R111 and catalase (KatGEsc) from Escherichia coli H736. Two immobilization methods and the conditions for one-step whole-cell catalysis of α-ketoglutaric acid were investigated. α-Ketoglutaric acid has broad applications in the pharmaceutical, food, and chemical industries. The specific research results are as follows: (1) By fusing the sfGFP tag, L-glutamate oxidase (LGOXStr r) and catalase (KatGEsc) were successfully anchored to the outer membrane of Escherichia coli cells, achieving one-step whole-cell catalysis of α-ketoglutaric acid with a conversion efficiency of up to 75%. (2) Through the co-immobilization of LGOXStr and KatGEsc, optimization of the preparation parameters of immobilized cells, and exploration of the immobilization method using E.coli@ZIF-8, immobilized cells with conversion rates of over 60% were obtained even after 10 cycles of reuse. Under the optimal conditions, the production rate of α-ketoglutaric acid reached 96.7% in a 12 h reaction, which is 1.1 times that of E. coli@SA and 1.29 times that of free cells.

Establishment of efficient 5-hydroxyvaleric acid production system by regenerating alpha-ketoglutaric acid and its application in poly(5-hydroxyvaleric acid) production

5-hydroxyvaleric acid (5-HV) is a versatile C5 intermediate of bio-based high-value chemical synthesis pathways. However, 5-HV production faces a few shortcomings involving the supply of cofactors, especially α-ketoglutaric acid (α-KG). Herein, we established a two-cell biotransformation system by introducing L-glutamate oxidase (GOX) to regenerate α-KG. Additionally, the catalase KatE was adapted to inhibit α-KG degradation by the H2O2 produced during GOX reaction. We searched for the best combination of genes and vectors and optimized the biotransformation conditions to maximize GOX effectiveness. Under the optimized conditions, 5-HV pathway with GOX showed 1.60-fold higher productivity than that of without GOX, showing 11.3 g/L titer. Further, the two-cell system with GOX and KatE was expanded to produce poly(5-hydroxyvaleric acid) (P(5HV)), and it reached at 412 mg/L of P(5HV) production and 20.5% PHA contents when using the biotransformation supernatant. Thus, the two-cell biotransformation system with GOX can potentially give the practical and economic alternative of 5-HV production using bio-based methods. We also propose direct utilization of 5-HV from bioconversion for P(5HV) production.

Glutamate oxidase-integrated biomimetic Fe3O4 hybrids as cascade nanozymes for glutamate detection

Herein, a new nanozyme/natural enzyme hybrid biosensor was established for ultrasensitive l-glutamic acid (L-Glu) detection. The Fe3O4 nanoparticles with peroxidase-like activity and stability was used as a nanozyme and carrier for immobilizing l-Glutamate oxidase (GLOD) through Schiffff base reaction to construct a chem-enzyme cascade detector. The resultant Fe3O4-GOLD exhibited a wide linear range (10−500 μM) and a low detection limit of 6.03 μM for L-Glu detection. Furthermore, the Fe3O4-GOLD exhibited excellent pH stability, thermal stability, reusability and storage stability. After repeated nine cycles, Fe3O4-GOLD still retained 70% of its initial activity. Meanwhile, Fe3O4-GOLD maintained 50% of its initial activity after storage for 20 days, while free GLOD only retained 20% of its initial activity. This strategy of integrating biomimetic Fe3O4 and natural enzymes for cascade catalysis makes it possible to design an efficient and stable chemo-enzyme composite catalysts, which are promising for applications in biosensing and biomimetic catalysis.

Efficient production of α-ketoglutaric acid using an economical double-strain cultivation and catalysis system.

The whole-cell catalysis strategy of alpha-ketoglutaric acid (α-KG) production from L-glutamic acid (L-Glu) using recombinant Escherichia coli, in which L-glutamate oxidase (LGox) was over-expressed, has replaced the traditional chemical synthesis strategy. However, large amounts of toxic by-product, H2O2, should be eliminated through co-expressing catalase (Cat), thus severely increasing burden in cells. To efficiently and economically produce α-KG, here, the genes SpLGox (from Streptomyces platensis NTU3304) and SlCat (from Streptomyces lividans TK24) were inserted into the low-dosage-IPTG (Isopropyl β-D-Thiogalactoside) inducible expression system, constructed in our previous work, in E. coli, respectively. Besides, a double-strain catalysis system was established and optimized to produce α-KG, and the productivity of α-KG was increased 97% compared with that through single strain catalysis. Finally, a double-strain cultivation strategy was designed and employed to simplify the scale-up fermentation. Using the optimized whole-cell biocatalyst conditions (pH 7.0, 35°C), majority of the L-glutamic acid was transformed into α-KG and the titer reached 95.4g/L after 6h with the highest productivity at present. Therefore, this strategy may efficiently and cost-effectively produce α-KG, enhancing its potential for industrial applications. KEY POINTS: • SpLGox and SlCat were over-expressed to catalyze L-Glu to α-KG and eliminate by-product H2O2, respectively. • Double-strain cultivation and catalysis system can efficiently and cost-effectively produce α-KG from L-Glu.

L-Glutamate Biosensor for In Vitro Investigations: Application in Brain Extracts

Investigations of L-glutamate release in living organisms can help to identify novel L-glutamate-related pathophysiological pathways, since abnormal transmission of L-glutamate can cause many neurological diseases. For the first time, a nitrogen-modified graphene oxide (GO) sample (RGO) is prepared through a simple and facile one-pot hydrothermal reduction of GO in the presence of 20 wt.% of the dye malachite green and is used for amperometric biosensing. The biosensor demonstrates adequate stability and is easy to prepare and calibrate. The biosensor detects the current generated during the electrooxidation of hydrogen peroxide released in the L-glutamate that is converted to the alpha-ketoglutarate catalyzed by L-glutamate oxidase. The biosensor consists of a semipermeable membrane, with L-glutamate oxidase (EC 1.4.3.11) immobilized in albumin and RGO and the working Pt electrode. First, the basic version of the L-glutamate biosensor is examined in PBS to investigate its sensitivity, reliability, and stability. To demonstrate the applicability of the L-glutamate biosensor in the analysis of complex real samples, quantification of L-glutamate in bovine brain extract is performed and the accuracy of the biosensor is confirmed by alternative methods. The enhanced version of the L-glutamate biosensor is applied for L-glutamate release investigations in a newly developed strain of rats (DAT-knockout, DAT-KO).

Development of a novel single-chain l-glutamate oxidase from Streptomyces sp. X-119–6 by inserting flexible linkers

L-glutamate oxidase (LGOX, EC: 1.4.3.11) is an oxidoreductase that catalyzes L-glutamate deamination. LGOX from Streptomyces sp. X-119–6 is used widely for L-glutamate quantification in research and industrial applications. This enzyme encoded as a single precursor chain that undergoes post-translational cleavage to four fragments by an endogenous protease to become highly active. Efficient preparation of active LGOX by heterologous expression without proteolysis process should be indispensable for wide application of this enzyme. Thus, developing an LGOX that requires no protease treatment should expand the potential applications of recombinant LGOX. In this report, we succeeded in obtaining an active single-chain LGOX by connecting the four fragments of the mature form with insertion of flexible linkers. The most active single-chain mutant showed the similar activity to that of the mature form from Streptomyces sp. X-119–6. The structure of this mutant was determined at 2.9 Å resolution by X-ray crystallography. It was revealed that this single-stranded mutant had the similar conformation to that of mature form. This single-chain LGOX can be produced efficiently and should expand LGOX applications.

A single-atom iron nanozyme reactor for α-ketoglutarate synthesis

Efficient removal of the by-product hydrogen peroxide (H2O2) in the oxidase-catalyzed reactions is a major challenge in biocatalysis that hinders the production of high yields of ketoacids. Here, we demonstrate the use of single-atom Fe nanozymes (SAFs) for H2O2 decomposition inspired by natural enzymes, to improve the efficiency of L-Glutamate oxidase (LGOX)-assisted catalysis for α-ketoglutarate (α-KG) synthesis. SAFs exhibit Metal-Nitrogen coordination and atomically dispersed active sites, providing superior enzyme-like activity for H2O2 decomposition. The SAFs@LGOX nanozyme-enzyme nanoreactors exhibit high catalytic efficiency due to in situ removal of H2O2 by SAFs during the deamination reaction. Additionally, SAFs enhance the pH and temperature tolerance, as well as thermal stability of LGOX. The nanoreactors achieved about 90% substrate conversion to α-KG within 2.5 h, compared to almost complete oxidation of the product in the absence of single atom Fe active sites. These findings suggest that the nanozyme-based strategy for rapid byproducts removal through mimicking enzymatic activity has promising applications in biocatalysis and may inspire the design of more effective nanozymes.

A biosensor based on oriented immobilization of an engineered l-glutamate oxidase on a screen-printed microchip for detection of l-glutamate in fermentation processes

This paper describes an amperometric biosensor utilizing an engineered l-glutamate oxidase for glutamate monitoring in microbial fermentation processes. We designed a general immobilization strategy that utilized a chitin-binding domain (ChBD-tag) as a biotether to further immobilize l-glutamate oxidase (GLOX) in an oriented manner on a screen-printed Prussian blue nanocube microchip (PB/SPC) with the biopolymer chitosan. The improved l-glutamate biosensor exhibited an enhanced sensitivity of 53.4 µA L mmol−1 cm−2 and a linear range from 25 µmol/L to 300 µmol/L with a detection limit of 9 µmol/L, and retained 95 % of its initial activity after two weeks of usage. In addition, the as-prepared biosensor was applied for real-time monitoring of food ingredient l-glutamate concentration during the fermentation process, which was in good agreement with that of high-performance liquid chromatography (HPLC). Above all, the l-glutamate biosensor prepared by this method had high analytical performance, and could fully realize real-time and high-efficiency monitoring in glutamate fermentation.

Vitreoscilla hemoglobin enhances the catalytic performance of industrial oxidases in vitro.

Oxidases are a group of oxidoreductases and need molecular oxygen in the catalytic process. Vitreoscilla hemoglobin (VHb) can improve the growth and productivity of host cells under hypoxic conditions, rendering it attractive for industrial application. In this work, we demonstrated the addition of immobilized VHb increased the catalytic activity of immobilized D-amino acid oxidase of Trigonopsis variabilis by two-fold when catalyzing cephalosporin C under oxygen-limited conditions. A similar increase of activities was observed in glucose oxidase, alcohol oxidase, and p-hydroxymandelate synthase by adding free VHb or immobilized VHb under hypoxic conditions. When L-glutamate oxidase was used to catalyze L-glutamate to produce α-ketoglutarate, the yield increased from 80.6 to 96.9% by fusing VHb with L-glutamate oxidase. Results demonstrated that the addition of free VHb, immobilized VHb, or fused VHb could increase the catalytic efficiency of oxidases, which was considered by increasing the concentration of the microenvironmental oxygen. Thus, VHb may become a potential additive agent to promote the efficiency of oxidases on industrial scale . KEY POINTS: • First time confirmation of facilitation of VHb on several industrial oxidases in vitro • VHb functions under hypoxic conditions rather than oxygen-enriched conditions • VHb functions in vitro in the form of free, immobilized protein and fusion enzyme.

Development of a glutaric acid production system equipped with stepwise feeding of monosodium glutamate by whole-cell bioconversion

In the bioproduction of glutaric acid, an emerging bioplastic monomer, α-ketoglutaric acid (α-KG) is required as an amine acceptor for 4-aminobutyrate aminotransferase (GabT)-driven conversion of 5-aminovalerate (5-AVA) to glutarate semialdehyde. Herein, instead of using expensive α-KG, an indirect α-KG supply system was developed using a relatively cheap alternative, monosodium glutamate (MSG), for l-glutamate oxidase (Gox)-based whole-cell conversion. Using 200 mM 5-AVA and 30 mM MSG initially with Gox, 67.1 mM of glutaric acid was produced. By applying the stepwise feeding strategy of MSG, the glutaric acid production capability was increased to 159.1 mM glutaric acid with a conversion yield of 79.6%. In addition, a buffer-free one-pot reaction from l-lysine was also applied in a 5 L bioreactor to evaluate its industrial applicability, resulting in a conversion yield of 54.2%. The system developed herein might have great potential for the large-scale, economically feasible production of glutaric acid by whole-cell conversion.

Molecular Structure, Spectroscopic Assessment, PDOS, Topology Evaluation and Docking Studies of 2-Chloro-5-nitrobenzophenone

The vibrational, electronic properties of 2-chloro-5-nitrobenzophenone (2C5NB) are explored experimentally, and theoretically (DFT) using B3LYP functional with LanL2DZ basis set. This has been performed for assignment vibrational frequencies that conjointly involves inserting beneficial evidence concerning the structure of the chosen compound. Based on PED, a comprehensive clarification of the FT-Infrared and FT-Raman spectra of the designated molecule were documented, with these studies agreeing satisfactorily with the experimental data. By mapping the total electron density isosurface with MEP, and contour map, charge density distribution and chemical reactivity spot of the 2C5NB were studied. Molecule stability ascending from hyper conjugative interactions and charge delocalization were explored using NBO analysis. For energies, the HOMO-LUMO diagram has been depicted. The transitions of the compound expression is (n→π*) in the UV-Vis region. The chemical changes of the molecule in 1H and 13C nuclear magnetic resonance were measured using the Gauge-Independent Atomic Orbital (GIAO) method and analysed using 1H and 13C NMR spectra. The non-zero value of μ and elevated β worth specify that the 2C5NB might be a good candidate for NLO content. In order to explore the simultaneous correlations of the different bonds of the 2C5NB, the total and partial DOS spectrum were intricated. Fukui functions were made to treasure the reactive site all over the molecule. The thermodynamic properties have been accomplished. The docking of molecule studies disclosed that the 2C5NB molecule performances a central role in binding proteins that inhibit L-glutamate oxidase. Minimum binding energy and intermolecular energy is perceived in the interaction.

Thermostability enhancement of l-glutamate oxidase from Streptomyces sp. NT1 by full consensus protein design

Thermostable l-glutamate oxidases (LGOXs) are desirable for use in l-glutamate (L-Glu) assay kits, enzymatic synthesis of α-ketoglutarate and for biosensor development. However, protein engineering efforts to improve thermostability often lead to a decrease in enzymatic activity. In this report, we aimed to enhance the thermostability (melting temperature, Tm) of a mesophilic LGOX from Streptomyces sp. NT1 (LGOXNT1) without a reduction in activity by a sequence-based protein design approach, termed full consensus (Fc) protein design. Among the 690 amino acids of LGOXNT1, 104 amino acids were substituted by the Fc protein design. The mutant gene was artificially synthesized and expressed in Escherichia coli BL21(DE3) cells. The Tm of the purified, recombinant LGOX mutant (FcLGOX) was determined to be ∼72°C, which is an increase on the Tm of 65°C for LGOXNT1 and the highest among known LGOXs. Importantly, purified FcLGOX showed no loss of specific activity or substrate specificity after a 30-min incubation at 70°C. Our findings provide a new approach to improve the thermostability of enzymes.

Obtaining L - Glutamate Oxidase Enzyme from Streptomyces and Estimation Its Toxicity on Blood Components

Streptomyces was isolated from the soil and then tested to diagnose morphologically and microscopically. Also, cultivated in the production medium of the L-glutamate oxidase enzyme, for which the wheat bran culture media was used, and then the extracellular L-glutamate oxidase enzyme was extracted using a cooling centrifuge at 8000 rpm for 20 minutes. The optimal temperature and pH for the production of the enzyme’s conditions were studied. Research results revealed that the optimum temperature for enzyme production was 30°C, and the best pH for the enzyme’s production was 7.0 later on, the enzyme was purified using common purification techniques represented by precipitation with ammonium sulfate as a preliminary purification step, followed by dialysis to remove salts, ion-exchange chromatography and gel filtration chromatography were used to finish purification process. The effect of the enzyme toxicity on the human blood components was evaluated. The enzyme had no harmful effect on the blood cells, with Red Blood Cells reaching 4 x 1012, White Blood Cells 7.5 × 109 and Platelets 293 × 109.

Abnormal glutamatergic neurotransmission and cognitive impairment in male APPNL-F/NL-F mice.

It is well established that glutamatergic neurotransmission plays an essential role in learning and memory. In Alzheimer's disease (AD), previous studies indicate that glutamate dynamics shift with disease progression, inciting cognitive impairment and further perpetuating disease pathology. Here, we build upon previous work by utilizing a novel knock-in mouse model of AD (APPNL-F/NL-F ) to characterize hippocampal glutamate signaling and cognition during late stage AD. At 18-24 months old, male APPNL-F/NL-F and genetic background control (C57BL/6) mice underwent cognitive assessment through a Morris water maze (MWM) task. Following MWM, basal and 70 mM KCl stimulus-evoked glutamate release was measured in the CA1 region of the hippocampus using a glutamate-selective microelectrode in isoflurane anesthetized mice. Briefly, microelectrodes were coated with L-glutamate oxidase for the detection of glutamate at the electrode surface. A layer of 1,3-phenylenediamine was applied to prevent detection of electroactive compounds at the recording potential (+0.7 volts). A micropipette (diameter = ∼20 µm) was attached 50-100 µm from the recording surface for local application of KCl). Calibration and recordings are taken using the FAST-16 recording software. Preliminary MWM data indicates no significant differences in spatial learning performance (corrected integrated path length and cumulative distance from the platform) between C57BL/6 and APPNL-F/NL-F mice. We observed a trend of decreased platform entries during the probe trial, supporting long-term spatial memory impairment in APPNL-F/NL-F mice. Preliminary in vivo CA1 data support a trend of decreased basal and stimulus-evoked glutamate levels in APPNL-F/NL-F mice compared to control mice. Preliminary findings support impaired long-term spatial memory and hypoactive glutamatergic neurotransmission in aged male APPNL-F/NL-F mice compared to age-matched C57BL/6 mice. Lack of glutamate activity in late-stage AD may underlie cognitive decline in APPNL-F/NL-F mice. Our laboratory previously observed similar findings in a transgenic AD model. However, unlike APPNL-F/NL-F mice, those mice also displayed increased basal glutamate levels. This divergence could be attributed to possible differences in glutamate transporter expression or activity with disease progression. Together, these data support loss of glutamate excitation with amyloid accumulation. Studies are ongoing.

Improvement of 2-phenylethanol production in Saccharomyces cerevisiae by evolutionary and rational metabolic engineering.

2-Phenylethanol (2-PE) is a valuable aromatic compound with favorable flavors and good properties, resulting in its widespread application in the cosmetic, food and medical industries. In this study, a mutant strain, AD032, was first obtained by adaptive evolution under 2-PE stress. Then, a fusion protein from the Ehrlich pathway, composed of tyrB from Escherichia coli, kdcA from Lactococcus lactis and ADH2 from Saccharomyces cerevisiae, was constructed and expressed. As a result, 3.14 g/L 2-PE was achieved using L-phenylalanine as a precursor. To further increase 2-PE production, L-glutamate oxidase from Streptomyces overexpression was applied for the first time in our research to improve the supply of α-ketoglutarate in the transamination of 2-PE synthesis. Furthermore, we found that the disruption of the pyruvate decarboxylase encoding gene PDC5 caused an increase in 2-PE production, which has not yet been reported. Finally, assembly of the efficient metabolic modules and process optimization resulted in the strain RM27, which reached 4.02 g/L 2-PE production from 6.7 g/L L-phenylalanine without in situ product recovery. The strain RM27 produced 2-PE (0.8 mol/mol) with L-phenylalanine as a precursor, which was considerably high, and displayed manufacturing potential regarding food safety and process simplification aspects. This study suggests that innovative strategies regarding metabolic modularization provide improved prospects for 2-PE production in food exploitation.

Extraction and Purification of Extracellular L-Glutamate Oxidase from Streptomyces.

The bacterial isolates Streptomyces were obtained from the soil and cultivated in a wheat bran medium, which was used to produce the L-glutamate oxidase enzyme. The extracellular enzyme was then extracted using a cooling centrifugation process to obtain the filtrate that represents the crude enzyme. Afterward, the enzyme purification processes were carried out which included precipitation with ammonium sulfate as a preliminary purification step followed by dialysis to remove the salts. Next, ion-exchange chromatography and gel filtration were used to finish the purification process, and the enzyme activity was determined for each purification step. The results of purification of L-glutamate oxidase enzyme from streptomyces using ammonium sulfate showed that the specific activity was 8.25 units/mg protein with a saturation ratio of 60%. Moreover, the results of purification using a dialysis tube indicated that the specific activity was 9.5 units/mg protein. In addition, the result of purification using diethylaminoethyl cellulose ion column revealed that the specific activity was 25 unit/mg protein and the results of purification using gel filtration showed that the specific activity was 56 units/mg protein which was the best step in the purification process due to high specific activity of the enzyme. The optimum temperature and pH for the activity and stability of the enzyme were tested. Based on the findings, the optimum temperature for the activity of the enzyme was 37 °C. In addition, it was found that the optimum temperature range for the stability of the enzyme was 30-50 °C. Besides, the optimum pH for the activity was 7.0 and the optimum pH range for the enzyme stability was 5.0-7.0.

Application of l-glutamate oxidase from Streptomyces sp. X119-6 with catalase (KatE) to whole-cell systems for glutaric acid production in Escherichia coli

Application of l-glutamate oxidase from Streptomyces sp. X119-6 with catalase (KatE) to whole-cell systems for glutaric acid production in Escherichia coli

A new l-arginine oxidase engineered from l-glutamate oxidase.

The alternation of substrate specificity expands the application range of enzymes in industrial, medical, and pharmaceutical fields. l-Glutamate oxidase (LGOX) from Streptomyces sp. X-119-6 catalyzes the oxidative deamination of l-glutamate to produce 2-ketoglutarate with ammonia and hydrogen peroxide. LGOX shows strict substrate specificity for l-glutamate. Previous studies on LGOX revealed that Arg305 in its active site recognizes the side chain of l-glutamate, and replacement of Arg305 by other amino acids drastically changes the substrate specificity of LGOX. Here we demonstrate that the R305E mutant variant of LGOX exhibits strict specificity for l-arginine. The oxidative deamination activity of LGOX to l-arginine is higher than that of l-arginine oxidase form from Pseudomonas sp. TPU 7192. X-ray crystal structure analysis revealed that the guanidino group of l-arginine is recognized not only by Glu305 but also Asp433, Trp564, and Glu617, which interact with Arg305 in wild-type LGOX. Multiple interactions by these residues provide strict specificity and high activity of LGOX R305E toward l-arginine. LGOX R305E is a thermostable and pH stable enzyme. The amount of hydrogen peroxide, which is a byproduct of oxidative deamination of l-arginine by LGOX R305E, is proportional to the concentration of l-arginine in a range from 0 to 100 μM. The linear relationship is maintained around 1 μM of l-arginine. Thus, LGOX R305E is suitable for the determination of l-arginine.