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1.
Biomater Sci ; 12(7): 1788-1800, 2024 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-38390988

RESUMO

Biofilms formed by pathogenic bacteria present a persistent risk to human health. While the eradication of matured biofilms remains a formidable challenge, delaying or preventing their formation, which is coordinately regulated by quorum sensing (QS), presents a simpler and more advantageous strategy. Quercetin, a naturally occurring compound with anti-QS properties, has the potential to act as an antibiofilm agent. However, it is plagued by certain inherent drawbacks, including poor water solubility and limited bioavailability. Furthermore, solely blocking QS is not enough to prevent biofilm formation because it lacks bactericidal properties. To address these difficulties, we fabricated bi-functional nanoparticles through the co-assembly of quercetin and copper ions in a facile manner. The resulting quercetin/copper nanoparticles (QC NPs) demonstrated minimal cytotoxicity and hemolysis in vitro. In response to the low pH of microenvironments that were populated by bacterial colonies, the QC NPs underwent disassembly to release copper ions and quercetin. The former exterminated bacteria by disrupting the integrity of the cell membrane, while the latter disrupted the processes involved in QS that are responsible for the biofilm by downregulating the expression of specific genes, effectively preventing the formation of biofilms by both Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. In addition, the QC NPs were integrated into a bacterial cellulose membrane. The composite membrane proved to be highly effective at inhibiting biofilm formation in vitro and demonstrated the ability to reduce inflammatory responses and accelerate the healing of bacteria-infected wounds in vivo. Overall, the bi-functional QC NPs hold great potential for use in addressing the challenges associated with the management of bacterial biofilms.


Assuntos
Nanopartículas , Percepção de Quorum , Humanos , Quercetina/farmacologia , Cobre/farmacologia , Biofilmes , Antibacterianos/farmacologia , Antibacterianos/química , Bactérias , Íons/farmacologia , Pseudomonas aeruginosa
2.
Crit Rev Food Sci Nutr ; : 1-16, 2023 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-37807720

RESUMO

The biosynthesis of functional sugars has gained significant attention due to their potential health benefits and increasing demand in the food industry. Enzymatic synthesis has emerged as a promising approach, offering high catalytic efficiency, chemoselectivity, and stereoselectivity. However, challenges such as poor thermostability, low catalytic efficiency, and food safety concerns have limited the commercial production of functional sugars. Protein engineering, including directed evolution and rational design, has shown promise in overcoming these barriers and improving biocatalysts for large-scale production. Furthermore, enzyme immobilization has proven effective in reducing costs and facilitating the production of functional sugars. To ensure food safety, the use of food-grade expression systems has been explored. However, downstream technologies, including separation, purification, and crystallization, still pose challenges in terms of efficiency and cost-effectiveness. Addressing these challenges is crucial to optimize the overall production process. Despite the obstacles, the future outlook for functional sugars is promising, driven by increasing awareness of their health benefits and continuous technological advancements. With further research and technological breakthroughs, industrial-scale production of functional sugars through biosynthesis will become a reality, leading to their widespread incorporation in various industries and products.

3.
Acta Biomater ; 170: 389-400, 2023 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-37625678

RESUMO

One of the serious threats to global public health is the bacterial biofilm, which results in numerous persistent and recurrent infections. Herein, we proposed a near-infrared (NIR) light-triggered "nano-domino" system with "dispersing and killing" functionality for biofilm eradication. The nanoplatform was fabricated by the self-assembly of chitosan conjugated with L-arginine (L-Arg, a natural nitric oxide (NO) donor) and indocyanine green (ICG, a phototherapy agent). Using an NIR irradiation "trigger", a series of reactive oxygen species (ROS) including singlet oxygen (1O2), hydrogen peroxide (H2O2), and superoxide anions (·O2-), as well as heat were generated from ICG aggregates. Subsequently, 1O2 and H2O2 catalyzed L-Arg to produce NO, which dispersed the biofilm and reacted with ·O2- to form peroxynitrite to kill bacteria with ROS collaboratively. Meanwhile, the generated heat increased the permeability of bacterial membranes, aggravating the damage to biofilm bacteria. The experiments on biofilm eradication demonstrated that this "nano-domino" system was capable to eradicate over 99.99% of biofilms formed by Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa under 5-min NIR irradiation. Notably, these integrated benefits allowed the system to promote the healing of MRSA biofilm-infected wounds in vivo with negligible toxicity. Overall, this reported NIR-triggered "nano-domino" system holds great promise for addressing the difficulties associated with bacterial biofilm eradication. STATEMENT OF SIGNIFICANCE: Novel agents for biofilm eradication are urgently needed due to the alarming rise in antimicrobial resistance to conventional antibiotics and the critical shortage of new drugs. In this study, we created a nano-domino system that uses near-infrared (NIR) light as a trigger to eradicate mature biofilms. In response to a short-term NIR irradiation, the proposed nanoplatform could generate nitric oxide and peroxynitrite to disperse the biofilm and kill the bacteria inside, respectively, leading to efficient eradication of Methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa biofilms with minimal cytotoxicity. The findings, therefore, indicate that this nanoplatform with enhanced antibiofilm performance might provide a reliable and promising solution to biofilm-related problems.

4.
Bioprocess Biosyst Eng ; 46(9): 1279-1291, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37450268

RESUMO

Cellobiose 2-epimerase (CE) is ideally suited to synthesize lactulose from lactose, but the poor thermostability and catalytic efficiency restrict enzymatic application. Herein, a non-characterized CE originating from Caldicellulosiruptor morganii (CmCE) was discovered in the NCBI database. Then, a smart mutation library was constructed based on FoldX ΔΔG calculation and modeling structure analysis, from which a positive mutant D226G located within the α8/α9 loop exhibited longer half-lives at 65-75 °C as well as lower Km and higher kcat/Km values compared with CmCE. Molecular modeling demonstrated that the improvement of D226G was largely attributed to the rigidification of the flexible loop, the compactness of the catalysis pocket and the increment of substrate-binding capability. Finally, the yield of synthesizing lactulose catalyzed by D226G reached 45.5%, higher than the 35.9% achieved with CmCE. The disclosed effect of the flexible loop on enzymatic stability and catalysis provides insight to redesign efficient CEs to biosynthesize lactulose.


Assuntos
Lactose , Lactulose , Lactulose/química , Lactose/química , Celobiose/química , Racemases e Epimerases/genética , Clostridiales , Desenho Assistido por Computador
5.
Macromol Biosci ; 23(11): e2300191, 2023 11.
Artigo em Inglês | MEDLINE | ID: mdl-37265089

RESUMO

Bacterial adhesion and subsequent biofilm formation on the surfaces of synthetic materials imposes a significant burden in various fields, which can lead to infections in patients or reduce the service life of industrial devices. Therefore, there is increasing interest in imbuing surfaces with antibacterial properties. Bioinspired superhydrophobic surfaces with high water contact angles (>150°) exhibit excellent surface repellency against contaminations, thereby preventing initial bacterial adhesion and inhibiting biofilm formation. However, conventional superhydrophobic surfaces typically lack long-term durability and are incapable of achieving persistent efficacy against bacterial adhesion. To overcome these limitations, in recent decades, dual-function superhydrophobic antibacterial surfaces with both bacteria-repelling and bacteria-killing properties have been developed by introducing bactericidal components. These surfaces have demonstrated improved long-term antibacterial performance in addressing the issues associated with surface-attached bacteria. This review summarizes the recent advancements of these dual-function superhydrophobic antibacterial surfaces. First, a brief overview of the fabrication strategies and bacteria-repelling mechanism of superhydrophobic surfaces is provided and then the dual-function superhydrophobic antibacterial surfaces are classified into three types based on the bacteria-killing mechanism: i) mechanotherapy, ii) chemotherapy, and iii) phototherapy. Finally, the limitations and challenges of current research are discussed and future perspectives in this promising area are proposed.


Assuntos
Bactérias , Aderência Bacteriana , Humanos , Propriedades de Superfície , Antibacterianos/farmacologia , Antibacterianos/química , Interações Hidrofóbicas e Hidrofílicas
6.
Appl Environ Microbiol ; 88(9): e0006222, 2022 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-35465694

RESUMO

d-Alanine belongs to nonessential amino acids that have diverse applications in the fields of food and health care. (R)-transaminase [(R)-TA]-catalyzed asymmetric amination of pyruvate is a feasible alternative for the synthesis of d-alanine, but low catalytic efficiency and thermostability limit enzymatic utilization. In this work, several potential (R)-TAs were discovered using NCBI database mining synchronously with enzymatic structure-function analysis, among which Capronia epimyces TA (CeTA) showed the highest activity for amination of pyruvate using (R)-α-methylbenzylamine as the donor. Furthermore, enzymatic residues surrounding a large catalysis pocket were subjected to saturation and combinatorial mutagenesis, and positive mutant F113T showed dramatic improvement in activity and thermostability. Molecular modeling indicated that the substitution of phenylalanine with threonine afforded alleviation of steric hindrance in the pocket and induced formation of additional hydrogen bonds with neighboring residues. Finally, using recombinant cells containing F113T as a biocatalyst, the conversion yield of amination of 100 mM pyruvate to d-alanine achieved up to 95.2%, which seemed to be the highest level in the literature regarding synthesis of d-alanine using TAs. The inherent characteristics rendered CeTA F113T a promising platform for efficient preparation of d-alanine operating with high productivity. IMPORTANCE d-Alanine is an important compound with many valuable applications. Its asymmetric synthesis employing (R)-ω-TA is considered an attractive choice. According to the stereoselectivity, ω-TAs have either (R)- or (S)-enantiopreference. There has been a variety of literature regarding screening, characterizing, and molecular modification of (S)-ω-TAs; in contrast, the research about (R)-ω-TA has lagged behind. In this work, we identify several (R)-ω-TAs and succeeded in creating mutant F113T, which showed not only better efficiency toward pyruvate but also higher thermostability compared with the original enzyme. The obtained original enzymes and positive mutants displayed important application value for pushing symmetric synthesis of d-alanine to a higher level.


Assuntos
Alanina , Transaminases , Alanina/metabolismo , Aminoácidos , Ascomicetos , Domínio Catalítico , Ácido Pirúvico/metabolismo , Transaminases/metabolismo
7.
Appl Microbiol Biotechnol ; 106(7): 2493-2501, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35348852

RESUMO

Obtaining a sucrose isomerase (SIase) with high catalytic performance is of great importance in industrial production of isomaltulose (a reducing sugar). In order to obtain such SIase mutant, a high-throughput screening system in microtiter plate format was developed based on a widely used 2,4-dinitrosalicylic acid (DNS) method for determination of reducing sugar. An SIase from Erwinia sp. Ejp617 (ErSIase) was selected to improve its catalytic efficiency. After screening of ~ 8000 mutants from a random mutagenesis library, Q209 and R456 were identified as beneficial positions. Saturation mutagenesis of the two positions resulted in a double-site mutant ErSIase_Q209S-R456H that showed the highest catalytic efficiency, and its specific activity reached 684 U/mg that is 17.5-fold higher than that of the wild-type ErSIase. By employing the lyophilized Escherichia coli (E. coli) cells harboring ErSIase_Q209S-R456H, a high space-time yield (STY = 3.9 kg/(L·d)) was achieved toward 600 g/L sucrose. Furthermore, the in silico analysis suggested that the hydrogen bond network was improved and steric hindrance was reduced due to the beneficial substitutions.Key points• A sucrose isomerase mutant with high catalytic efficiency was obtained.• The highest space-time yield was achieved toward high-concentration sucrose.• The optimized H-bond network contributed to the enhanced catalytic efficiency.


Assuntos
Escherichia coli , Isomaltose , Escherichia coli/genética , Glucosiltransferases , Isomaltose/análogos & derivados , Isomaltose/química , Sacarose
8.
Biotechnol Bioeng ; 119(3): 845-856, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34928500

RESUMO

Biocatalysis in high-concentration organic solvents (OSs) offers many advantages, but realizing this process remains a huge challenge. An R-selective ω-amine transaminase variant (AcATAM2 ) exhibited high activity toward 50 g/L pro-sitagliptin ketone 1-[1-piperidinyl]-4-[2,4,5-trifluorophenyl]-1,3-butanedione (PTfpB). However, AcATAM2 displayed unsatisfactory organic-cosolvent resistance against high-concentration dimethyl sulfoxide (DMSO), which is required to enhance the solubility of the hydrophobic substrate PTfpB. Located in the substrate-binding tunnel, enzyme gates are structural elements that undergo reversible conformational transitions, thus affecting the accessibility of the binding pocket to solvent molecules. Depending on the conformation of the enzyme gates, one can define an open or closed conformation on which the enzyme activity in OSs may depend. To enhance the DMSO resistance of AcATAM2 , we identified the beneficial residues at the "enzyme gate" region via computational analysis, alanine scanning, and site-saturation mutagenesis. Two beneficial variants, namely, AcATAM2F56D and AcATAM2F56V , not only displayed improved enzyme activity but also exhibited enhanced DMSO resistance (the half-life value increased from 25.71 to 42.49 h under 60% DMSO). Molecular dynamic simulations revealed that the increase in DMSO resistance was mainly caused by the decrease in the number of DMSO molecules in the substrate-binding pocket. Moreover, in the kilogram-scale experiment, the conversion of 80 g/L substrate was increased from 50% (AcATAM2 ) to 85% (M2F56D in 40% DMSO) with a high e.e. of >99% within 24 h.


Assuntos
Dimetil Sulfóxido , Simulação de Dinâmica Molecular , Biocatálise , Dimetil Sulfóxido/química , Solventes/química , Transaminases/genética
9.
Appl Biochem Biotechnol ; 193(11): 3624-3640, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34347249

RESUMO

ω-Transaminase (ω-TA) is an attractive biocatalyst for stereospecific preparation of amino acids and derivatives, but low catalytic efficiency and unfavorable substrate specificity hamper their industrial application. In this work, to obtain applicable (R)-ω-TA responsible for amination of α-keto acids substrates, the reactivities of eight previously synthesized ω-TAs toward pyruvate using (R)-α-methylbenzylamine ((R)-α-MBA) as amine donor were investigated, and Gibberella zeae TA (GzTA) with the highest (R)-TA activity and stereoselectivity was selected as starting scaffold for engineering. Site-directed mutagenesis around enzymatic active pocket and access tunnel identified three positive mutation sites, S214A, F113L, and V60A. Kinetic analysis synchronously with molecular docking revealed that these mutations afforded desirable alleviation of steric hindrance for pyruvate and α-MBA. Furthermore, the constructed single-, double-, and triple-mutant exhibited varying degrees of improved specificities toward bulkier α-keto acids. Using 2-oxo-2-phenylacetic acid (1d) as substrate, the conversion rate of triple-mutant F113L/V60A/S214A increased by 3.8-fold relative to that of wide-type GzTA. This study provided a practical engineering strategy for improving catalytic efficiency and substrate specificity of (R)-ω-TA. The obtained experience shed light on creating more industrial ω-TAs mutants that can accommodate structurally diverse substrates.


Assuntos
Aminoácidos/síntese química , Mutagênese Sítio-Dirigida , Transaminases , Aminoácidos/química , Domínio Catalítico , Especificidade por Substrato/genética , Transaminases/química , Transaminases/genética
10.
Sheng Wu Gong Cheng Xue Bao ; 37(7): 2351-2365, 2021 Jul 25.
Artigo em Chinês | MEDLINE | ID: mdl-34327901

RESUMO

Concrete is the most widely used modern building material. It is easy to crack under the action of stress, which makes the concrete structure permeable, affecting the durability and integrity of the structure, and thus shortening its service life. Microbial in-situ remediation technology is a low cost, effective and green way for concrete crack repairing. Due to its excellent biocompatibility, service life elongation, economic losses and environmental pollution reduction, microbial in-situ remediation technology has been intensively investigated. Bacillus has attracted much attention because of its excellent biomineralization ability, extremely strong environmental tolerance and long-term survival ability of its spores. In order to promote the research, development and large-scale application of microbial in-situ healing of concrete, the paper reviews the mechanism of spore-based in-situ healing of concrete, the survival of spores exposed in concrete, the influence of spores and external additives on the mechanical properties of concrete, progress in research and development of healing agent as well as healing effects. Moreover, future research focuses such as improving the survival ability of spores in the harsh environment of concrete, reducing the influence of external additives on the mechanical properties of concrete, and strengthening the healing effect of actual field applications are also summarized.


Assuntos
Bacillus , Carbonato de Cálcio , Materiais de Construção , Esporos Bacterianos , Tecnologia
12.
Pharm Biol ; 59(1): 303-310, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33715588

RESUMO

CONTEXT: Physcion (Phy) exerts several pharmacological effects including anti-inflammatory, antioxidant, and antitumor properties. OBJECTIVE: This study investigates the cytotoxicity and its underlying mechanisms of Phy on breast cancer. MATERIALS AND METHODS: Human breast cancer cell MCF-7 was treated with 5-400 µM Phy for 24 h, MCF-7-xenografted BALB/c nude mice and immunosuppressive mice model induced by cyclophosphamide were intraperitoneally injected with 0.1 mL/mouse normal saline (control group) and 30 mg/kg Phy every other day for 14 or 28 days, and pathological examination, ELISA and western blot were employed to investigate the Phy anti-breast cancer property in vitro and in vivo. RESULTS: In MCF-7 cells, Phy 24 h treatment significantly reduced the cell viability at dose of 50-400 µM and 24 h, with an IC50 of 203.1 µM, and 200 µM Phy induced 56.9, 46.9, 36.9, and 46.9% increment on LDH and caspase-3, -8 and -9. In MCF-7-xenograft tumour nude mice and immunosuppressive mice, 30 mg/kg Phy treatment inhibited tumour growth from the 8th day, and reduced Bcl-2 and Bcl-xL >50%, HO-1 and SOD-1 > 70% in tumour tissues of immunosuppressive mice. In addition, Phy reduced nuclear factor erythroid 2-related factor 2 > 30% and its downstream proteins, and enhanced the phosphorylation of nuclear factor-kappa B > 110% and inhibitor of NF-кB α > 80% in the tumour tissues of BALB/c mice. DISCUSSION AND CONCLUSIONS: This research demonstrated that Phy has an anti-breast cancer property via the modulation of oxidative stress-mediated mitochondrial apoptosis and immune response, which provides a scientific basis for further research on its clinical applications.


Assuntos
Antineoplásicos/farmacologia , Neoplasias da Mama/tratamento farmacológico , Emodina/análogos & derivados , Estresse Oxidativo/efeitos dos fármacos , Animais , Antineoplásicos/administração & dosagem , Apoptose/efeitos dos fármacos , Neoplasias da Mama/patologia , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Emodina/administração & dosagem , Emodina/farmacologia , Feminino , Humanos , Imunidade/efeitos dos fármacos , Concentração Inibidora 50 , Células MCF-7 , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto
13.
Biotechnol Lett ; 43(1): 261-269, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32910357

RESUMO

OBJECTIVE: To characterize a recombinant isomerase that can catalyze the isomerization of sucrose into isomaltulose and investigate its application for the enzymatic production of isomaltulose. RESULTS: A sucrose isomerase gene from Erwinia sp. Ejp617 was synthesized and expressed in Escherichia coli BL21(DE3). The enzymatic characterization revealed that the optimal pH and temperature of the purified sucrose isomerase were 6.0 and 40 °C, respectively. The enzyme activity was slightly activated by Mn2+and Mg2+, but partially inhibited by Ca2+, Ba2+, Cu2+, Zn2+ and EDTA. The kinetic parameters of Km and Vmax for sucrose were 69.28 mM and 118.87 U/mg, respectively. The time course showed that 240.9 g/L of isomaltulose was produced from 300 g/L of sucrose, and the yield reached 80.3% after bioreaction for 180 min. CONCLUSIONS: This recombinant enzyme showed excellent capability for biotransforming sucrose to isomaltulose at the substrate concentration of 300 g/L. Further investigations should be carried out focusing on selection of suitable heterologous expression system with the aim to improve its expression level.


Assuntos
Proteínas de Bactérias , Glucosiltransferases , Isomaltose/análogos & derivados , Proteínas Recombinantes , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Proteínas de Bactérias/metabolismo , Biotransformação , Estabilidade Enzimática , Erwinia/enzimologia , Erwinia/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Glucosiltransferases/química , Glucosiltransferases/genética , Glucosiltransferases/isolamento & purificação , Glucosiltransferases/metabolismo , Isomaltose/análise , Isomaltose/química , Isomaltose/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , Proteínas Recombinantes/metabolismo
14.
Enzyme Microb Technol ; 141: 109655, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33051014

RESUMO

The creation of an R-selective ω-amine transaminase (ω-ATA) as biocatalyst is crucial for the asymmetric amination of prochiral ketones to produce sitagliptin intermediates because rare ω-ATAs are R-selective in nature and most of them suffer from poor stability and low activity toward bulky prochiral ketones. Here, the gene of an R-selective ω-ATA was cloned from Arthrobacter cumminsii ZJUT212 (AcATA) and expressed in Escherichia coli. The best variants (M1 + M122H and M1+T134 G) were obtained using a semi-rational protein design after screening. These variants not only exhibited improved activity and substrate affinity but also enhanced stability in aqueous phase containing 20 % dimethyl sulfoxide. The conversion of asymmetric amination on 50 g/L pro-sitagliptin ketone PTfpB (1-[1-piperidinyl]-4-[2,4,5-trifluorophenyl]-1,3-butanedione) achieved 92 %, with an extremely high e.e. of >99 %, using 2 gDCW/L E. coli cells harboring M1 + M122H as biocatalyst. In the kilogram-scale experiment, approximately 40 kg of (R)-APTfpB (e.e. >99 %) was produced within 30 h when 50 kg PTfpB was used as the substrate. Furthermore, the space-time yield reached ≈32 g/(L·d).


Assuntos
Aminas/metabolismo , Fosfato de Sitagliptina/metabolismo , Transaminases/metabolismo , Aminação , Aminas/química , Biocatálise , Estabilidade Enzimática , Escherichia coli/genética , Cetonas/química , Cetonas/metabolismo , Cinética , Micrococcaceae/enzimologia , Micrococcaceae/genética , Simulação de Dinâmica Molecular , Mutagênese , Engenharia de Proteínas , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Fosfato de Sitagliptina/química , Estereoisomerismo , Especificidade por Substrato , Transaminases/química , Transaminases/genética
15.
Bioprocess Biosyst Eng ; 43(9): 1599-1607, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32333194

RESUMO

Transaminase responsible for alienating prochiral ketone compound is applicable to asymmetric synthesis of herbicide L-phosphinothricin (L-PPT). In this work, the covalent immobilization of recombinant transaminase from Citrobacter koseri (CkTA) was investigated on different epoxy resins. Using optimum ES-105 support, a higher immobilized activity was obtained via optimizing immobilization process in terms of enzyme loading, coupling time and initial PLP concentration. Crucially, due to blocking unreacted epoxy groups on support surface with amino acids, the reaction temperature of blocked immobilized biocatalyst was enhanced from 37 to 57 °C. Its thermostability at 57 °C was also found to be superior to that of free CkTA. The Km value was shifted from 36.75 mM of free CkTA to 39.87 mM of blocked immobilized biocatalyst, demonstrating that the affinity of enzyme to the substrate has not been apparently altered. Accordingly, the biocatalyst performed the consecutive synthesis of L-PPT for 11 cycles (yields>91%) with retaining more than 91.13% of the initial activity. The seemingly the highest reusability demonstrates this biocatalyst has prospective for reducing the costs of consecutive synthesis of L-PPT with high conversion.


Assuntos
Aminobutiratos/síntese química , Proteínas de Bactérias/química , Citrobacter koseri/enzimologia , Enzimas Imobilizadas/química , Resinas Epóxi/química , Transaminases/química , Proteínas de Bactérias/genética , Citrobacter koseri/genética , Enzimas Imobilizadas/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Transaminases/genética
16.
J Biotechnol ; 302: 10-17, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31201835

RESUMO

α-Transaminase (α-TA) responsible for catalyzing the reversible transfer of amino groups between amine donors and amine acceptors, is applicable to enzymatic route for asymmetric synthesis of herbicide l-phosphinothricin (l-PPT). In the search for α-TAs with better catalysis performance, three α-TAs were discovered by genome mining approach using a known sequence encoding Escherichia coli tyrosine TA (TyrB) as probe. Through detailed comparison of their expression amount, activities and characteristics, Citrobacter koseri TA (CkTA) exhibited better activity and thermostability, which retain 65.9% of initial activity after incubation at 57 °C for 4 h. The Km and kcat/Km values of CkTA were 36.75 mM and 34.29 mM-1 min-1, respectively. In addition, recombinant CkTA cells were immobilized onto Celite 545 using tris(hydroxymethyl)phosphine as crosslinker. During five repetitive asymmetric synthesis of l-PPT from 20 g/L prostereogenic ketone using l-Glu as amine donor, all the yields of l-PPT reached up to 91.2% (>99% ee). These characteristics made CkTA a valuable addition to the currently scarce α-TA library for stereospecific synthesis of l-PPT.


Assuntos
Aminobutiratos/metabolismo , Citrobacter koseri/enzimologia , Transaminases/metabolismo , Biotecnologia/métodos , Estabilidade Enzimática , Temperatura
17.
Bioresour Technol ; 285: 121344, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30999186

RESUMO

In this study, recombinant E. coli BL21(DE3)/pCDFDuet-1-XR-GDH harboring xylose reductase (XR) and glucose dehydrogenase (GDH) were immobilized and applied for the production of xylitol from xylose mother liquor (XML). Various immobilization methods were screened and the cross-linking approach with diatomite and polyetherimide as the raw materials and glutaraldehyde as the cross-linking agent was the optimal one, and the recovery activity reached of 80.3% after immobilization. The half-life of immobilized cells was 1.52 times to that of free cells. Batch experiments showed that the enzyme activity of immobilized cells remained 70.5% of the initial activity after 10 batches and the space-time yield of xylitol reached of 11.5 g/(L h). The production of xylitol from xylose mother liquor by immobilized E. coli cells containing xylose reductase and glucose dehydrogenase was reported for the first time, which paved a foundation for industrial production of xylitol from waste xylose mother liquor.


Assuntos
Xilitol , Xilose , Aldeído Redutase , D-Xilulose Redutase , Escherichia coli , Feminino , Fermentação , Glucose , Glucose 1-Desidrogenase , Humanos , Mães
18.
J Biosci Bioeng ; 126(2): 176-182, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29627319

RESUMO

Glucose isomerase (GI) responsible for catalyzing the isomerization from d-glucose to d-fructose, was an important enzyme for producing high fructose corn syrup (HFCS). In a quest to prepare HFCS at elevated temperature and facilitate enzymatic recovery, an effective procedure for whole cell immobilization of refractory Thermus oshimai glucose isomerase (ToGI) onto Celite 545 using tris(hydroxymethyl)phosphine (THP) as crosslinker was established. The immobilized biocatalyst showed an activity of approximate 127.3 U/(g·immobilized product) via optimization in terms of cells loading, crosslinker concentration and crosslinking time. The pH optimum of the immobilized biocatalyst was displaced from pH 8.0 of native enzyme to neutral pH 7.0. Compared with conventional glutaraldehyde (GLU)-immobilized cells, it possessed the enhanced thermostability with 70.1% residual activity retaining after incubation at 90°C for 72 h. Moreover, the THP-immobilized biocatalyst exhibited superior operational stability, in which it retained 85.8% of initial activity after 15 batches of bioconversion at 85°C. This study paved a way for reducing catalysis cost for upscale preparation of HFCS with higher d-fructose concentration.


Assuntos
Aldose-Cetose Isomerases , Enzimas Imobilizadas , Xarope de Milho Rico em Frutose/metabolismo , Temperatura Alta , Fosfinas/química , Aldose-Cetose Isomerases/química , Aldose-Cetose Isomerases/metabolismo , Reagentes de Ligações Cruzadas/química , Reagentes de Ligações Cruzadas/farmacologia , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Frutose/química , Frutose/metabolismo , Glucose/química , Glucose/metabolismo , Xarope de Milho Rico em Frutose/química , Concentração de Íons de Hidrogênio , Fosfinas/metabolismo , Fosfinas/farmacologia
19.
Chem Biol Interact ; 283: 51-58, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29408431

RESUMO

Aucubin, an iridoid glycoside found in several plants, such as Eucommia ulmoide and Rehmannia, has various pharmacological effects. Bone formation is a complex process in which osteoblast differentiation plays an important role. This study aimed to investigate the promotion effects of aucubin on osteoblast differentiation in MG63 cells, a human osteoblast-like cell line. Aucubin not only improved osteoblast differentiation, as shown by enhanced ALP (alkaline phosphatase) concentration and mineralization in cells, but increased the expression of various cytokines, including collagen I, osteocalcin, osteopontin, integrin ß1, and Osterix. Aucubin strongly enhanced the levels of BMP2 (bone morphogenetic proteins-2) in MG63 cells, which play a central role during osteoblast differentiation. Further data show that aucubin exposure after 1 day, 7 days, and 14 days enhanced the expression of Smad1, 5, and 8, and the phosphoresced levels of MAPKs (mitogen-activated protein kinases) family Erk (extracellular signal-regulated kinases), JNK (c-Jun-NH2-terminal kinases), P38, and Akt (serine/threonine protein kinase)/mTOR (mammalian target of rapamycin)/p70s6k in MG63 cells. This study shows the improved effects of aucubin on osteoblast differentiation in MG63 cells, related to the signaling of BMP2-mediated Smads (drosophila mothers against decapentaplegic proteins), MAPKs, and Akt/mTOR/p70S6K. This study indicates the potential of aucubin for osteoporosis treatment.


Assuntos
Proteína Morfogenética Óssea 2/metabolismo , Diferenciação Celular/efeitos dos fármacos , Glucosídeos Iridoides/farmacologia , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Colágeno Tipo I/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Humanos , Glucosídeos Iridoides/química , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Osteoblastos/metabolismo , Osteocalcina/metabolismo , Osteopontina/metabolismo , Fosforilação/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteína Smad1/metabolismo , Proteína Smad5/metabolismo , Proteína Smad8/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo
20.
Sci Rep ; 7(1): 8402, 2017 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-28827748

RESUMO

Calf Spleen Extractive Injection (CSEI), extracted from the spleen of healthy cows (within 24 hours of birth), is a small-peptide-enriched extraction and often used as an ancillary agent in cancer therapy. This study evaluated the hematopoietic function of CSEI and its underlying mechanisms, principally in CHRF, K562 cells, BMNCs and a mouse model of cyclophosphamide (CTX)-induced hematopoietic suppression. CSEI promoted the proliferation and differentiation of CHRF and K562 cells, activated hematopoietic- and proliferation-related factors RSK1p90, ELK1 and c-Myc, and facilitated the expression of differentiation- and maturation-related transcription factors GATA-1, GATA-2. In the mice with hematopoietic suppression, 3 weeks of CSEI administration enhanced the bodyweights and thymus indices, suppressed the spleen indices and strongly elevated the production of HSPCs, neutrophils and B cells in bone marrow, ameliorated bone marrow cellularity, and regulated the ratio of peripheral blood cells. Proteome profiling combined with ELISA revealed that CSEI regulated the levels of cytokines, especially G-CSF and its related factors, in the spleen and plasma. Additional data revealed that CSEI promoted phosphorylation of STAT3, which was stimulated by G-CSF in both mice spleen and cultured BMNCs. Taken together, CSEI has the potential to improve hematopoietic function via the G-CSF-mediated JAK2/STAT3 signaling pathway.


Assuntos
Extratos Celulares/administração & dosagem , Proliferação de Células/efeitos dos fármacos , Ciclofosfamida/toxicidade , Fator Estimulador de Colônias de Granulócitos/metabolismo , Janus Quinase 2/metabolismo , Fator de Transcrição STAT3/metabolismo , Transdução de Sinais , Animais , Animais Recém-Nascidos , Medula Óssea/efeitos dos fármacos , Bovinos , Diferenciação Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Ciclofosfamida/administração & dosagem , Ensaio de Imunoadsorção Enzimática , Humanos , Injeções , Camundongos , Proteoma/análise , Baço/química
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