The high content of sucrose and raffinose reduces the prebiotic value of soybean oligosaccharides. Fructan sucrases can catalyze the conversion of sucrose and raffinose to high-value products such as fructooligosaccharides and melibiose. To obtain a fructan sucrase that can efficiently convert soybean oligosaccharides, we first mined the fructan sucrase gene from microorganisms in the coastal areas of Xisha Islands and Bohai Bay and then characterized the enzymatic and catalytic properties of the enzyme. Finally, recombinant extracellular expression of this gene was carried out in Bacillus subtilis. The results showed that a novel fructan sucrase, BhLS 39, was mined from Bacillus halotolerans. With sucrose and raffinose as substrates, BhLS 39 showed the optimal temperatures of 50 ℃ and 55 ℃, optimal pH 5.5 for both, and K_cat/K_m ratio of 3.4 and 6.6 L/(mmol·s), respectively. When 400 g/L raffinose was used as the substrate, the melibiose conversion rate was 84.6% after 30 min treatment with 5 U BhLS 39. Furthermore, BhLS 39 catalyzed the conversion of sucrose to produce levan-type-fructooligosaccharide and levan. Then, the recombinant extracellular expression of BhLS 39 in B. subtilis was achieved. The co-expression of the intracellular chaperone DnaK and the extracellular chaperone PrsA increased the extracellular activity of the recombinant BhLS 39 by 5.2 folds to 17 U/mL compared with that of the control strain. BhLS 39 obtained in this study is conducive to improving the quality and economic benefits of soybean oligosaccharides. At the same time, the strategy used here to enhance the extracellular expression of BhLS 39 will also promote the efficient recombinant expression of other proteins in B. subtilis.
Oligosaccharides/metabolism* ; Glycine max/metabolism* ; Bacillus subtilis/metabolism* ; Sucrase/biosynthesis* ; Raffinose/metabolism* ; Fructans/metabolism* ; Sucrose/metabolism* ; Bacillus/genetics* ; Recombinant Proteins/biosynthesis* ; Bacterial Proteins/biosynthesis*

A novel β-glucosidase BglD2 with glucose and ethanol tolerant properties was screened and cloned from the deep-sea bacterium Bacillus sp. D1. The application potential of BglD2 toward polydatin-hydrolyzing was also evaluated. BglD2 exhibited the maximal β-glucosidase activity at 45 °C and pH 6.5. BglD2 maintained approximately 50% of its origin activity after incubation at 30 °C and pH 6.5 for 20 h. BglD2 could hydrolyze a variety of substrates containing β (1→3), β (1→4), and β (1→6) bonds. The activity of β-glucosidase was enhanced to 2.0 fold and 2.3 fold by 100 mmol/L glucose and 150 mmol/L xylose, respectively. BglD2 possessed ethanol-stimulated and -tolerant properties. At 30 °C, the activity of BglD2 enhanced to 1.2 fold in the presence of 10% ethanol and even remained 60% in 25% ethanol. BglD2 could hydrolyze polydatin to produce resveratrol. At 35 °C, BglD2 hydrolyzed 86% polydatin after incubation for 2 h. Thus, BglD2 possessed glucose and ethanol tolerant properties and can be used as the potential candidate of catalyst for the production of resveratrol from polydatin.
Enzyme Stability ; Glucose ; Glucosides/pharmacology* ; Hydrogen-Ion Concentration ; Stilbenes/pharmacology* ; Substrate Specificity ; Temperature ; Xylose ; beta-Glucosidase/genetics*

Trametes versicolor has strong ability to degrade environmental organic pollutants. NADPH-cytochrome P450 reductase (CPR) of T. versicolor transfers electron to cytochrome P450s (CYPs) and participates in the degradation process of organic pollutants. Sequence analysis showed that the genome of T. versicolor contains 1 potential CPR and multiple potential CYP sequences. To further study the molecular mechanism for the involvement of T. versicolor CPR in the cellular degradation of organic pollutants, a CPR gene from T. versicolor was cloned and heterologously expressed in Escherichia coli. Subsequently, the main properties of the recombinant enzyme were investigated. A truncated CPR protein lacking the predicted membrane anchor region (residues 1-24), named CPRΔ24, was overexpressed as a soluble form in E. coli. The recombinant CPRΔ24 protein showed a molecular weight consistent with the theoretical value of 78 kDa. Recombinant CPRΔ24 was purified using a Ni²⁺-chelating column followed by size exclusion chromatography. The specific activity of the purified CPRΔ24 was 5.82 U/mg. The CPRΔ24 enzyme displayed the maximum activity at 35 ℃ and pH 8.0. It has different degrees of tolerance against several types of metal ions and organic solvents. The apparent Km and kcat values of recombinant CPRΔ24 for NADPH were 19.7 μmol/L and 3.31/s, respectively, and those for the substrate cytochrome c were 25.9 μmol/L and 10.2/s, respectively, under conditions of 35 ℃ and pH 8.0. The above research provides the basis for exploring the functional mechanism of T. versicolor CPR in the degradation pathway of environmental organic pollutants.

In producing recombinant β-glucosidase in Escherichia coli by high-cell density cultivation (HCDC), insufficient soluble oxygen is always a problem. To address it, Vitreoscilla hemoglobin (VHb) was introduced into Escherichia coli by the bicistron and T₇ promoter expression systems, to improve soluble oxygen by bacterial cells and thereby to enhance the biomass and recombinant β-glucosidase production. In the case of bicistron expression system, cell density in shaking flask reached OD₆₀₀=(4.24±0.29), 35.03% higher than that of the control without VHb. Correspondingly, the maximum activity of β-glucosidase co-expressed with VHb was (9.78±0.55) U/mL, 25.38% higher than that of the control. In a 3-L fermentor, the maximum activity of β-glucosidase was 141.23 U/mL, 35.57% higher than that of the control. In contrast, the activity of β-glucosidase co-expressed with VHb under T₇ promoter was lower than that of the control, either in flask or in fermentor. Co-expressing β-glucosidase with VHb using the bicistron expression system may improve the tolerance of E. coli to insufficient soluble oxygen and thus promote the bacterial biomass and the enzyme yield.

Laccase is a widely-used environment-friendly copper-containing oxidase found in many plants, insects and fungi. Recently, more and more laccases are also found in bacteria. Myxobacteria are an important bacteria resource. However, myxobacteria are much more difficult to isolate and purify than other bacteria. We used bioinformatic approach to screen myxobacteria proteomes available in NCBI. Based on conserved sequences of four copper binding sites in multicopper oxidase, 30 potential laccase sequences were obtained. Among them, nine genes were synthesized and expressed in Escherichia coli BL21 (DE3). Seven proteins showed laccase activity when tested with traditional laccase substrates. One protein, named rSC-2, was chosen for further research because it exhibited the highest activity towards 2,6-dimethyl phenol (DMP). The molecular weight of rSC-2 was 57 kDa. Its specific activity to DMP was 0.27 U/mg. The optimal temperature and the optimal pH were 60 ℃ and 7.0, respectively. About 50% of the original activity was retained after incubation at 60 ℃ and pH 7.0-8.0 for 1 h. Metals showed different effects on rSC-2. rSC-2 activity was enhanced by several metalsat concentration of 1 mmol/L, such as Ca²⁺ and Mn²⁺. With a higher concentration of 5 mmol/L, the activity of rSC-2 was apparently inhibited. This is the first report of bioinformatics screening myxobacteria laccases in combination with expression in E. coli.

We isolated and identified the symbiotic and adnascent microorganisms from an unidentified sponge collected from 10-meter-deep seawater of the Paracel Islands in China. A total of 16 strains were obtained and identified. Through bacteriostatic activity assay, one of the strains, Dermacoccus sp. X4, was found to effectively inhibit the growth of Staphylococcus aureus. Subsequently, its secondary metabolites were purified by silica gel partition, octadecylsilane (ODS) reverse phase, Sephadex™LH-20 size exclusion, and C18 reverse phase chromatography. Using liquid chromatography, mass spectrometry, and nuclear magnetic resonance, three of the purified compounds were structurally characterized to be one 3-(4-hydroxybenzyl) hexahydropyrrolo [1,2-a]pyrazine-1,4-dione and two indole acid glycerides. This is the first report about indole acid glyceride isolated from microbial secondary metabolites, enriching marine drug candidate resources.
Actinomycetales ; chemistry ; Animals ; China ; Chromatography, Liquid ; Indoles ; isolation & purification ; pharmacology ; Magnetic Resonance Spectroscopy ; Mass Spectrometry ; Porifera ; microbiology ; Seawater ; Secondary Metabolism ; Staphylococcus aureus ; drug effects

We screened for laccase from a marine metagenomic library and obtained a bacterial laccase Lac15 and studied its decolorization ability. Using synthetic azo dyes and anthraquinonic dyes as substrates, we investigated the dye decolorization ability of recombinant Lac15 (rLac15). The purified rLac15 had better decolorization ability towards the azo dyes than the anthraquinonic dyes. When incubated at 45 degrees C and pH 8.5 for 1 h with methylsyringate as the mediator, 20 U/L of rLac15 could decolorize 95% of 100 micromol/L Acid Red 6B (AR-6B), 93% of Reactive Blue 194 (M-2GE), 76% of Reactive Brilliant Orange (K-7R) and 66% of Reactive Blue 171 (KE-R). The decolorization ability of rLac15 decreased with the dye concentration increasing. However, more than 80% of M-2GE and AR-6B were degraded even when the dye concentration was up to 200 micromol/L. At room temperature, rLac51 exhibited significant decolorization ability, with 96% of AR-6B, 86% of M-2GE, 66% of K-7R and 66% of KE-Rdegraded within 24 h at 25 degrees C. rLac15 has the potential of industrial applications.
Anthraquinones ; isolation & purification ; Azo Compounds ; isolation & purification ; Bacteria ; enzymology ; isolation & purification ; Biodegradation, Environmental ; Coloring Agents ; isolation & purification ; Escherichia coli ; genetics ; metabolism ; Laccase ; genetics ; metabolism ; Recombinant Proteins ; genetics ; metabolism ; Seawater ; microbiology ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

The purpose of this paper is to establish sulfhydryl site-directed PEGylation method for lysostaphin and to evaluate effects of mutagenesis and modification of amino acid residue within putative linker on enzyme activity. On the basis of structural analysis of lysostaphin, amino acid 133-154 of tentative linker between the N-terminal and C-terminal domain were chosen as the candidate residues for site-directed mutagenesis to cysteine. Subsequently, sulfhydryl site-directed PEGylation was performed by reacting PEG-maleimide reagent with the newly introduced cysteine residue of the mutant lysostaphin. The Cys-mutant and PEG-modified proteins were both purified, and their enzymatic activity were further PEGylated lysostaphins. The mono-PEGylated lysostaphins were separated from unmodified lysostaphins through highly efficient one step method with Ni(2+)-NTA column chromatography. However, both Cys-mutant and PEGylated lysostaphin only retained partial activities of the wild-type enzyme. It suggests that sulfhydryl site-directed PEGylation modification of the tentative linker between the N-terminal and C-terminal domain may affect the catalytic activity of lysostaphin.
Anti-Infective Agents, Local ; chemistry ; metabolism ; Base Sequence ; Catalysis ; Cysteine ; chemistry ; genetics ; metabolism ; Escherichia coli ; genetics ; metabolism ; Lysostaphin ; biosynthesis ; chemistry ; metabolism ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Mutant Proteins ; chemistry ; metabolism ; Polyethylene Glycols ; chemistry ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism ; Staphylococcus ; metabolism ; Sulfhydryl Reagents ; pharmacology

Laccases (benzenediol: oxygen oxidoreductases; EC 1.10.3.2) are copper-containing polyphenol oxidases that can oxidize a wide range of aromatic compounds, concomitantly with the transfer of four electrons and the reduction of molecular oxygen to water. The progress on the research of laccases structure and function is reviewed. Their three-dimensional structures and catalytic mechanism, as well as their applications in different fields are emphasized.
Catalysis ; Hydrocarbons, Aromatic ; isolation & purification ; metabolism ; Laccase ; chemistry ; metabolism ; Oxidation-Reduction

The G13 domain derived from granulysin shows high antimicrobial activities against Gram-positive and Gram-negative bacteria but does not lyse Jurkat cells or liposomes. To explore a new approach for high expression of the G13 domain, we fused the sequence encoding G13 to thioredoxin (Trx) gene to construct the recombinant expression vector (pThioHisA-G13). A cyanogen bromide (CNBr) cleavage site was introduced between the Trx and G13 to facilitate final release of the recombinant G13. The recombinant expression vector, pThioHisA-G13, was transformed into E. coli BL21 (DE3). Upon induction by IPTG Trx-G13 fusion protein was expressed and took the form of inclusion bodies counting 58% (W/W) of total cellular proteins. The inclusion body was solved by urea (8 mol/L) and then cleaved by CNBr. We purified the recombinant peptide G13 by one-step cation exchange chromatography. Results of agarose diffuse assay analysis indicated that the recombinant G13 exhibited antibacterial activity. The procedure described in this study will provide a reliable and simple method for highly efficient production of some cationic antimicrobial peptides.
Anti-Infective Agents ; metabolism ; Antigens, Differentiation, T-Lymphocyte ; genetics ; Cyanogen Bromide ; pharmacology ; Escherichia coli ; genetics ; metabolism ; GTP-Binding Protein alpha Subunits, G12-G13 ; biosynthesis ; genetics ; Inclusion Bodies ; metabolism ; Protein Structure, Tertiary ; genetics ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; Thioredoxins ; genetics ; Transfection