Anti-proliferative, anti-migration, and anti-invasion activity of novel hesperidin glycosides in non-small cell lung cancer A549 cells.

Background and purpose: Several attempts have been made to synthesize and investigate modified flavonoids to improve their potential anticancer efficacy. This study aimed to determine the in vitro anti-viability, anti-migration, and anti-invasive effects of two novel hesperidin glycosides, hesperidin glucoside (HG1) and hesperidin maltoside (HG2), compared to original hesperidin and diosmin. Experimental approach: Inhibitory effects on normal (MRC5) and cancer (A549) cell viability of hesperidin glycosides were investigated by the trypan blue and MTS assays. A scratch assay determined the suppressive effects on cancer cell migration, and inhibition of cancer cell invasion was investigated through Matrigel™. The selectivity index (SI), a marker of cell toxicity, was also determined for A549 relative to MRC5 cells. Findings/Results: The cell viability trypan blue and MTS assays showed similar results of the inhibition of A549 cancer cells; HG1 and HG2 had lower IC50 than original hesperidin and diosmin. The SI of HG1 and HG2 was > 2 after 72-h culture. Investigation of cell migration showed that HG1 and HG2 inhibited the ability of gap closure in a time- and dose-dependent manner. The infiltration of the Matrigel™-coated filter by A549 cells was suppressed in the presence of HG1 and HG2. This result implied that HG1 and HG2 could inhibit cancer cell invasion. Conclusion and implication: Our results suggest the inhibition of cancer cell migration and invasion in a time- and concentration-related manner with a favorable toxic profile. Moreover, HG1 and HG2 appeared potentially better agents than the original hesperidin for future anticancer development.

Enzymatic Synthesis of Maltitol and Its Inhibitory Effect on the Growth of Streptococcus mutans DMST 18777.

This study aimed to synthesize maltitol using recombinant CGTase from Bacillus circulans A11 with ß-cyclodextrin (ß-CD) and sorbitol as a glucosyl donor and acceptor, respectively, and assess its antibacterial activity. Optimal conditions for producing the highest yield, 25.0% (w/w), were incubation of 1% (w/v) ß-CD and sorbitol with 400 U/mL of CGTase in 20 mM phosphate buffer at pH 6.0 and 50 °C for 72 h. Subsequently, maltitol underwent large-scale production and was purified by HPLC. By mass spectrometry, the molecular weight of the synthesized maltitol was 379.08 daltons, corresponding exactly to that of standard maltitol. The relative sweetness of synthesized and standard maltitol was ~90% of that of sucrose. Spot assay on the agar plate showed that maltitol inhibited the growth of Streptococcus mutans DMST 18777 cells. In addition, the MIC and MBC values of synthesized and standard maltitol against S. mutans were also determined as 20 and 40 mg/mL, respectively. These results show that the synthesized maltitol can be produced at high yields and has the potential to be used as an anticariogenic agent in products such as toothpaste.

Heterologous expression of 4α-glucanotransferase: overproduction and properties for industrial applications.

4α-Glucanotransferase (4α-GTase) is unique in its ability to form cyclic oligosaccharides, some of which are of industrial importance. Generally, low amount of enzymes is produced by or isolated from their natural sources: animals, plants, and microorganisms. Heterologous expressions of these enzymes, in an attempt to increase their production for applicable uses, have been widely studied since 1980s; however, the expressions are mostly performed in the prokaryotic bacteria, mostly Escherichia coli. Site-directed mutagenesis has added more value to these expressed enzymes to display the desired properties beneficial for their applications. The search for further suitable properties for food application leads to an extended research in expression by another group of host organism, the generally-recognized as safe host including the Bacillus and the eukaryotic yeast systems. Herein, our review focuses on two types of 4α-GTase: the cyclodextrin glycosyltransferase and amylomaltase. The updated studies on the general structure and properties of the two enzymes with emphasis on heterologous expression, mutagenesis for property improvement, and their industrial applications are provided.

Optimization of amylomaltase for the synthesis of α-arbutin derivatives as tyrosinase inhibitors.

α-Arbutin is widely used as a skin-whitening agent in the pharmaceutical and cosmetic industries because of its inhibitory effect on tyrosinase, an important enzyme for generating melanin pigments. Given the increasing demand for such products, we synthesized α- and ß-arbutin-α-D-glycosides through transglycosylation reactions catalyzed by a recombinant amylomaltase, using tapioca starch and α- and ß-arbutin as donor and acceptor molecules, respectively. The catalytic yield of products by the amylomaltase was greater with α-arbutin than with ß-arbutin. The highest glycoside yield (83%) was achieved by adjusting the following six parameters: starch and α-arbutin concentration, enzyme concentration, pH, temperature, and incubation time. The glycoside products were isolated and analyzed by HPLC, and two major products were identified by mass spectrometry and nuclear magnetic resonance spectroscopy, namely, α-arbutin-α-d-glucopyranoside (α-Ab-α-G1) and α-arbutin-α-d-maltopyranoside (α-Ab-α-G2). Both α-Ab-α-G1 and α-Ab-α-G2 are more water soluble than α-arbutin. Like α-arbutin, α-Ab-α-G1 and α-Ab-α-G2 showed competitive inhibition of human tyrosinase. However, their Ki values were 0.53 and 1.40 mM, respectively, which are slightly higher than that of α-arbutin (0.25 mM). The addition of glucosyl residues to α-arbutin improved its water solubility. Therefore, α-Ab-α-G1 and α-Ab-α-G2 could be easily absorbed by the skin and used as skin-whitening agents in pharmaceutical and cosmetic industries.

Roles of N287 in catalysis and product formation of amylomaltase from Corynebacterium glutamicum.

Amylomaltase catalyzes intermolecular and intramolecular transglucosylation reactions to form linear and cyclic oligosaccharides, respectively. The aim of this work is to investigate the structure-function relationship of amylomaltase from a mesophilic Corynebacterium glutamicum (CgAM). Site-directed mutagenesis was performed to substitute Tyr for Asn287 (N287Y) to determine its role in controlling amylomaltase activity and product formation. Expression of the wild-type (WT) and N287Y was achieved by cultivating recombinant cells in the medium containing lactose at 16 °C for 14 h. The purified mutated enzyme showed a significant decrease in all transglucosylation activities while hydrolysis activity was not changed. Optimum temperature and pH for disproportionation reaction were slightly changed upon mutation while those for cyclization reaction were not changed. Interestingly, N287Y showed a change in large-ring cyclodextrin (LR-CD) product profile in which the larger size was observed together with an increase in thermostability and substrate preference for G5 in addition to G3. The secondary structure of the mutated enzyme was slightly changed in related to the WT as evidenced from circular dichroism analysis. This work thus demonstrates that N287 is required for transglucosylation activities of CgAM. Having an aromatic residue in this position increased thermostability, changed product profile and substrate preference but demolished most enzyme activities.

Application of amylomaltase for the synthesis of salicin-α-glucosides as efficient anticoagulant and anti-inflammatory agents.

The focus of this study was the synthesis of α-glucosyl derivatives of salicin by a transglucosylation reaction. The reaction was catalyzed by recombinant amylomaltase using tapioca starch as a glucosyl donor. Several reaction parameters, such as the enzyme-substrate concentrations, pH, temperature and incubation time, were optimized. Using the optimum conditions, at least three products with retention times (Rt) of 6.2, 9.2 and 14.1 were observed. The maximum yield of glucosylated salicin derivatives was 63% (w/w) of the total products. The structures of the glucosylated salicin derivatives were confirmed to be salicin-α-D-glucopyranoside, salicin-α-D-maltopyranoside and salicin-α-D-maltotriopyranoside through a combination of enzyme treatments, mass spectrometry and NMR analyses. The glycosidic bond between glucose units consisted of an α-1,4-configuration. The water solubility of salicin-α-D-glucopyranoside, salicin-α-D-maltopyranoside and salicin-α-D-maltotriopyranoside was 3-, 5- and 8-fold higher, respectively, than that of salicin, whereas their relative sweetness values were lower than that of sucrose. Interestingly, the long-chain salicin-α-D-glucosides showed greater anticoagulant and anti-inflammatory activities than salicin. In addition, the synthesized salicin-α-D-glucosides were able to tolerate acidic and high temperature conditions, but not α-glucosidase or human digestive enzymes. Therefore, these salicin-α-D-glucosides should be applied by the injection route to achieve greater bioavailability than is possible by the oral route.

Mutagenesis for improvement of activity and thermostability of amylomaltase from Corynebacterium glutamicum.

This work aims to improve thermostability of amylomaltase from a mesophilic Corynebacterium glutamicum (CgAM) by random and site-directed mutagenesis. From error prone PCR, a mutated CgAM with higher thermostability at 50 °C compared to the wild-type was selected and sequenced. The result showed that the mutant contains a single mutation of A406V. Site-directed mutagenesis was then performed to construct A406V and A406L. Both mutated CgAMs showed higher intermolecular transglucosylation activity with an upward shift in the optimum temperature and a slight increase in the optimum pH for disproportionation and cyclization reactions. Thermostability of both mutated CgAMs at 35-40 °C was significantly increased with a higher peak temperature from DSC spectra when compared to the wild-type. A406V had a greater effect on activity and thermostability than A406L. The catalytic efficiency values kcat/Km of A406V- and A406L-CgAMs were 2.9 and 1.4 times higher than that of the wild-type, respectively, mainly due to a significant increase in kcat. LR-CD product analysis demonstrated that A406V gave higher product yield, especially at longer incubation time and higher temperature, in comparison to the wild-type enzyme.

Altered large-ring cyclodextrin product profile due to a mutation at Tyr-172 in the amylomaltase of Corynebacterium glutamicum.

Corynebacterium glutamicum amylomaltase (CgAM) catalyzes the formation of large-ring cyclodextrins (LR-CDs) with a degree of polymerization of 19 and higher. The cloned CgAM gene was ligated into the pET-17b vector and used to transform Escherichia coli BL21(DE3). Site-directed mutagenesis of Tyr-172 in CgAM to alanine (Y172A) was performed to determine its role in the control of LR-CD production. Both the recombinant wild-type (WT) and Y172A enzymes were purified to apparent homogeneity and characterized. The Y172A enzyme exhibited lower disproportionation, cyclization, and hydrolysis activities than the WT. The k(cat)/K(m) of the disproportionation reaction of the Y172A enzyme was 2.8-fold lower than that of the WT enzyme. The LR-CD product profile from enzyme catalysis depended on the incubation time and the enzyme concentration. Interestingly, the Y172A enzyme showed a product pattern different from that of the WT CgAM at a long incubation time. The principal LR-CD products of the Y172A mutated enzyme were a cycloamylose mixture with a degree of polymerization of 28 or 29 (CD28 or CD29), while the principal LR-CD product of the WT enzyme was CD25 at 0.05 U of amylomaltase. These results suggest that Tyr-172 plays an important role in determining the LR-CD product profile of this novel CgAM.

Kinetic inhibition of human salivary alpha-amylase by a novel cellobiose-containing tetrasaccharide.

OBJECTIVE: The aim of the study was to evaluate the inhibitory kinetics of a novel cellobiose-containing tetrasaccharide on human salivary alpha-amylase (HSA). MATERIAL AND METHOD: Synthesis of cellobiose-containing tetrasaccharide was catalyzed by Paenibacillus sp. All CGTase using beta-CD as a donor and cellobiose as an acceptor under the optimal conditions. The reaction mixture was analyzed by HPLC and a cellobiose-containing tetrasaccharide obtained was studied for its inhibitory kinetics. RESULTS: In vitro activity of human salivary alpha-amylase showed the optimum pH and temperature at 7.0 and 37 degrees C, respectively. The effects of metal ions, protective chemicals and saccharides on alpha-amylase activity, they were found that 10 mM concentration of CaCl2 and NaCl enhanced the enzyme activity. In contrast, the enzyme activity was significantly inhibited by 10 mM of HgCI2, alpha-cyclodextrin (alpha-CD) and synthetic cellobiose-containing tetrasaccharide. Chemicals often used as protective substance for enzyme such as beta-mercaptoethanol, EDTA or used as fungicide during enzyme purification (NaN3) had no effect on the activity of this enzyme. As a cellobiose-containing tetrasaccharide was shown to have a pronounce inhibition on alpha-amylase activity. Its inhibition kinetic was performed and found that cellobiose-containing tetrasaccharide was a competitive inhibitor with a Ki value of 7.89 microM. CONCLUSION: Inhibition kinetic of a cellobiose-containing tetrasaccharide on alpha-amylase activity was competitive type with Ki value of 7.89 microM. In addition, these results will be a basic knowledge in controlling alpha-amylase actions that have influence on blood glucose level of trial animal and human further

Expression and characterization of a fusion protein-containing cyclodextrin glycosyltransferase from Paenibacillus sp. A11.

A recombinant cyclodextrin glycosyltransferase (CGTase) gene fused with thioredoxin (Trx), hexa-histidine (His(6)) and S-protein (S) at the N terminus and a proline-rich peptide (PRP) at the C terminus, was constructed using the wild-type gene from Paenibacillus sp. A11, the pET-32a vector and Escherichia coli BL21(DE3) as the host cell. The expression levels and enzyme characteristics of the Trx-His(6)-CGTase-PRP fusion protein, the recombinant CGTase without fusion peptides, and the wild-type CGTase were compared. The maximum specific activity for the Trx-His(6)-CGTase-PRP fusion enzyme was 2.7 fold higher than that of the non-fusion form at the optimal IPTG concentration. The Trx-His(6)-CGTase-PRP fusion protein was purified to homogeneity by starch adsorption and Ni-NTA affinity chromatography, with a specific activity of 2,268 units/mg protein at a 61% yield. The ease of purification and the higher enzyme yield were obtained with the fusion form when compared to the non-fusion and wild-type enzymes. The fusion enzyme was superior than its wild-type counterpart in terms of stability against high temperature and organic solvents. Moreover, the fusion enzyme could catalyze the synthesis of cyclodextrins in 20% (v/v) dimethylformamide with a higher product yield of CD(7) and CD(8) compared to that of the wild-type enzyme in the same buffer-solvent system.

Altered product specificity of a cyclodextrin glycosyltransferase by molecular imprinting with cyclomaltododecaose.

Cyclodextrin glycosyltransferases (CGTases), members of glycoside hydrolase family 13, catalyze the conversion of amylose to cyclodextrins (CDs), circular alpha-(1,4)-linked glucopyranose oligosaccharides of different ring sizes. The CD containing 12 alpha-D-glucopyranose residues was preferentially synthesized by molecular imprinting of CGTase from Paenibacillus sp. A11 with cyclomaltododecaose (CD(12)) as the template molecule. The imprinted CGTase was stabilized by cross-linking of the derivatized protein. A high proportion of CD(12) and larger CDs was obtained with the imprinted enzyme in an aqueous medium. The molecular imprinted CGTase showed an increased catalytic efficiency of the CD(12)-forming cyclization reaction, while decreased k(cat)/K(m) values of the reverse ring-opening reaction were observed. The maximum yield of CD(12) was obtained when the imprinted CGTase was reacted with amylose at 40 degrees C for 30 min. Molecular imprinting proved to be an effective means toward increase in the yield of large-ring CDs of a specific size in the biocatalytic production of these interesting novel host compounds for molecular encapsulations.

Effect of temperature on cyclodextrin production and characterization of paracetamol/cyclodextrin complexes.

OBJECTIVE: To compare the effect of different reaction temperatures on the cyclization and coupling reactions of the Toruzyme CGTase influencing the yield of cyclodextrins (CDs) and to study the solubility of paracetamol with CDs. MATERIAL AND METHOD: Type and amount of CDs were analyzed by HPAEC-PAD. The stability constants for the inclusion complex formed between CDs and paracetamol were determined using the phase solubility method. The solubility of paracetamol with CDs was measured by UV-spectrophotometer at 240 nm. RESULTS: The result has shown that the reaction temperature has effect on the Toruzyme CGTase reactions in production of CDs. The CDs yield after 30 min of incubation was higher at 60 degrees C than at 80 degrees C. The catalytic efficiency (k(cat)/K(m)) of this enzyme indicated the higher value of the cyclization reaction at 60 degrees C compared to 80 degrees C while the opposite was found for the coupling reaction. Paracetamol is used as an analgesic and antipyretic but it is poorly water-soluble drug. To improve the solubility of paracetamol CDs obtained were used to study for paracetamol/CDs complexes. The phase-solubility diagrams of paracetamol with alpha-, beta- and gamma-CD were A(N) type while that of paracetamol with maltosyl-beta-CD (G2-beta-CD) complex was A(L) type. The stability constants (K(c)) for the inclusion complex of paracetamol with alpha-, beta-, gamma-CD and G2-beta-CD were 5.69, 16.75, 4.73 and 2,223.25 M(-1), respectively. CONCLUSION: The optimum temperature for CDs production was at 60 degrees C and the low solubility of paracetamol was significantly improved by complexation with CDs, where the enhancing effect was in the order of G2-beta-CD > beta-CD > alpha-CD > gamma-CD.

Purification and characterization of two alkaline, thermotolerant alpha-amylases from Bacillus halodurans 38C-2-1 and expression of the cloned gene in Escherichia coli.

A newly isolated strain, 38C-2-1, produced alkaline and thermotolerant alpha-amylases and was identified as Bacillus halodurans. The enzymes were purified to homogeneity and named alpha-amylase I and II. These showed molecular masses of 105 and 75 kDa respectively and showed maximal activities at 50-60 degrees C and pH 10-11, and 42 and 38% relative activities at 30 degrees C. These results indicate that the enzymes are thermotolerant. The enzyme activity was not inhibited by a surfactant or a bleaching reagent used in detergents. A gene encoding alpha-amylase I was cloned and named amyI. Production of AmyI with a signal peptide repressed the growth of an Escherichia coli transformant. When enzyme production was induced by the addition of isopropyl beta-D(-)-thiogalactopyranoside in the late exponential growth phase, the highest enzyme yield was observed. It was 45-fold that of the parent strain 38C-2-1.

Molecular imprinting of cyclodextrin glycosyltransferases from Paenibacillus sp. A11 and Bacillus macerans with gamma-cyclodextrin.

Cyclodextrin glycosyltransferase catalyzes the formation of a mixture of cyclodextrins from starch by an intramolecular transglycosylation reaction. To manipulate the product specificity of the Paenibacillus sp. A11 and Bacillus macerans cyclodextrin glycosyltransferases towards the preferential formation of gamma-cyclodextrin (CD(8)), crosslinked imprinted proteins of both cyclodextrin glycosyltransferases were prepared by applying enzyme imprinting and immobilization methodologies. The crosslinked imprinted cyclodextrin glycosyltransferases obtained by imprinting with CD(8) showed pH and temperature optima similar to those of the native and immobilized cyclodextrin glycosyltransferases. However, the pH and temperature stability of the immobilized and crosslinked imprinted cyclodextrin glycosyltransferases were higher than those of the native cyclodextrin glycosyltransferases. When the catalytic activities of the native, immobilized and crosslinked imprinted cyclodextrin glycosyltransferases were compared, the efficiency of the crosslinked imprinted enzymes for CD(8) synthesis was increased 10-fold, whereas that for cyclodextrin hydrolysis was decreased. Comparison of the product ratios by high-performance anion exchange chromatography showed that the native cyclodextrin glycosyltransferases from Paenibacillus sp. A11 and Bacillus macerans produced CD(6) : CD(7) : CD(8) : > or = CD(9) ratios of 15 : 65 : 20 : 0 and 43 : 36 : 21 : 0 after 24 h of reaction at 40 degrees C with starch substrates. In contrast, the crosslinked imprinted cyclodextrin glycosyltransferases from Paenibacillus sp. A11 and Bacillus macerans produced cyclodextrin in ratios of 15 : 20 : 50 : 15 and 17 : 14 : 49 : 20, respectively. The size of the synthesis products formed by the crosslinked imprinted cyclodextrin glycosyltransferases was shifted towards CD(8) and > or = CD(9), and the overall cyclodextrin yield was increased by 12% compared to the native enzymes. The crosslinked imprinted cyclodextrin glycosyltransferases also showed higher stability in organic solvents, retaining 85% of their initial activity after five cycles of synthesis reactions.

Expression of cyclodextrinase gene from Paenibacillus sp. A11 in Escherichia coli and characterization of the purified cyclodextrinase.

The expression of the Paenibacillus sp. A11 cyclodextrinase (CDase) gene using the pUC 18 vector in Escherichia coli JM 109 resulted in the formation of an insoluble CDase protein in the cell debris in addition to a soluble CDase protein in the cytoplasm. Unlike the expression in Paenibacillus sp. A11, CDase was primarily observed in cytoplasm. However, by adding 0.5 M sorbitol as an osmolyte, the formation of insoluble CDase was prevented while a three-fold increase in cytoplasmic CDase activity was achieved after a 24 h-induction. The recombinant CDase protein was purified to approximately 14-fold with a 31% recovery to a specific activity of 141 units/mg protein by 40-60% ammonium sulfate precipitation, DEAE-Toyopearl 650 M, and Phenyl Sepharose CL-4B chromatography. It was homogeneous by non-denaturing and SDS-PAGE. The enzyme was a single polypeptide with a molecular weight of 80 kDa, as determined by gel filtration and SDS-PAGE. It showed the highest activity at pH 7.0 and 40 degrees C. The catalytic efficiency (k(cat)/K(m)) values for alpha-, beta-, and gamma- CD were 3.0 x 10(5), 8.8 x 10(5), and 5.5 x 10(5) M(-1) min(-1), respectively. The enzyme hydrolyzed CDs and linear maltooligosaccharides to yield maltose and glucose with less amounts of maltotriose and maltotetraose. The rates of hydrolysis for polysaccharides, soluble starch, and pullulan were very low. The cloned CDase was strongly inactivated by N-bromosuccinimide and diethylpyrocarbonate, but activated by dithiothreitol. A comparison of the biochemical properties of the CDases from Paenibacillus sp. A11 and E. coli transformant (pJK 555) indicates that they were almost identical.

Identification of an alkaline-tolerant cyclodextrin-metabolizing bacterium and characterization of its cyclodextrinase gene.

Bacillus circulans A11, an alkaline-tolerant cyclodextrin-metabolizing bacterium isolated from South-East Asian soil, was reidentified as Paenibacillus sp. A11 based on 16S rRNA gene sequence comparison, G + C content and cellular fatty acid composition. Levels of similarity of the 16S rRNA gene between strain A11 and the Paenibacillus species were 90-99%, while similarity with Bacillus circulans was only 86%. The major cellular fatty acid was anteiso-C15:0 which accounted for 59.3% of the total cellular fatty acids and the G+C content was 50.3 mol%. The CDase gene coding for this enzyme was cloned into E. coli. The open reading frame of the CDase gene was 1,959 bp encoding a CDase of 653 amino acid residues. At maximum growth, the specific activity of the recombinant CDase from E. coli was higher than that of Paenibacillus sp. A11. By SDS-PAGE, the translation product of the recombinant gene showed the same mobility as the purified CDase from the original strain. CDase from both Paenibacillus sp. A11 and E. coli produced glucose and maltose as dominant end-products of beta-CD hydrolysis. The ratio of maltose to glucose was 1:2.

Identification of essential histidines in cyclodextrin glycosyltransferase isoform 1 from Paenibacillus sp. A11.

The isoform 1 of cyclodextrin glycosyltransferase (CGTase, EC 2.4.1.19) from Paenibacillus sp. A11 was purified by a preparative gel electrophoresis. The importance of histidine, tryptophan, tyrosine, and carboxylic amino acids for isoform 1 activity is suggested by the modification of the isoform 1 with various group-specific reagents. Activity loss, when incubated with diethylpyrocarbonate (DEP), a histidine modifying reagent, could be protected by adding 25 mM methyl-beta-cyclodextrin substrate prior to the modification. Inactivation kinetics of isoform 1 with DEP resulted in second-order rate constants (k(inactivation)) of 29.5 M(-1)s(-1). The specificity of the DEP-modified reaction for the histidine residue was shown by the correlation between the loss of isoform activity and the increase in the absorbance at 246 nm of N-carbethoxyhistidine. The number of histidines that were modified by DEP in the absence and presence of a protective substrate was estimated from the increase in the absorbance using a specific extinction coefficient of N-carbethoxyhistidine of 3,200 M(-1)cm(-1). It was discovered that methyl-beta-CD protected per mole of isoform 1, two histidine residues from the modification by DEP. To localize essential histidines, the native, the DEP-modified, and the protected forms of isoform 1 were digested by trypsin. The resulting peptides were separated by HPLC. The peptides of interest were those with R(t) 11.34 and 40.93 min. The molecular masses of the two peptides were 5,732 and 2,540 daltons, respectively. When the data from the peptide analysis were checked with the sequence of CGTase, then His-140 and His-327 were identified as essential histidines in the active site of isoform 1.