To investigate the mechanism of high product specificity of gamma-clodextrin glucanotransferase (CGTase) from alkalophilic Bacillus clarkii 7364, we aligned protein sequence and structure model, found out that loss of 6 amino acids at subsite -7 probably affected its product specificity. Using overlapping PCR method, we inserted 6 amino acids into subsite -7 of CGTase. The mutant CGTase gene was ligated with pET-20b (+) and expressed in Escherichia coli BL21 (DE3). The extracellular recombinant enzyme was used to transform soluble starch into cyclodextrins (CDs). HPLC analysis results show that, compared to wild CGTase, the gamma-CDs produced by mutant enzyme decreased from 76.0% to 12.5%, whereas the ratio of alpha- and beta-CDs increased from 8.7% and 15.2% to 37.5% and 50%. The possible mechanism was that, compared to alpha-, beta-CGTase, wild gamma-CGTase lacks 6 amino acids in its subsite -7. This conformation provided more space for glucose combination and was thus advantageous for forming gamma-CD. When the 6 amino acids were inserted into the subsite -7 of wild gamma-CGTase, the space to bind with glucose reduced and consequently resulted in less gamma-CD production.
Bacillus ; enzymology ; genetics ; Escherichia coli ; genetics ; metabolism ; Glucosyltransferases ; biosynthesis ; genetics ; Mutant Proteins ; biosynthesis ; genetics ; Recombinant Proteins ; biosynthesis ; genetics

Recently, the interactions between hepatitis C virus (HCV) genes and the host cell factors were the focus of this field. Cell factors in the different biochemical pathway were approved to be interfered when HCV infection. To make sure which HCV gene(s) was the major factor during the interaction process, ten eukaryotic expression plasmids containing different functional genes of HCV: Core, E1, E2, p7, NS2, NS3, NS4A, NS4B, NS5A and NS5B were transfected into the CHO-K1 cells respectively. Then ten stable cell lines expressing different HCV functional proteins were constructed under the selective pressure of G418. DNA and mRNA of the HCV genes were both detected by PCR and RT-PCR respectively in the corresponding stable cell lines, freezation and anabiosis would not lose the HCV genes. Besides, the El, E2 and NS5B proteins were detected by Western-blot which demonstrated that the HCV genes have formed stable expression in the host cells. The activity of UDP-glucose ceramide glucosyltransferase (UGCG) in the stable cell lines increased in different degree by TLC assay. For example, the activity of UGCG in CHO-K1-E2 and CHO-K1-p7 was doubled according to the control cells,and in CHO-K1-NS2 and CHO-K1-NS5A was about 1.6 times compared with the control cells. The establishment of the stable cell lines containing different single HCV gene will provide foundation for investigating the interactions between the virus and the host factors, and for the filtration of antiviral medicine.
Animals ; CHO Cells ; Cricetinae ; Cricetulus ; Glucosyltransferases ; biosynthesis ; metabolism ; Hepacivirus ; genetics ; metabolism ; Transfection ; Viral Envelope Proteins ; biosynthesis ; genetics ; Viral Nonstructural Proteins ; biosynthesis ; genetics ; Viral Proteins ; biosynthesis ; genetics

Trehalose, a compatible solute, is widely used in food, cosmetics, pharmaceutical products and organ transplantation. Nowadays, trehalose is mostly produced by enzymatic synthesis with many secondary products and lowpurity. In this study, high amount of trehalose was produced by recombinant E. ccli fermentation. First, a bifunctional trehalose gene TPSP was amplified from genome of C. hutchinscoii. Second, an expression vector pTac-HisA containing TPSP was constructed and transformed into the host E. coli. Expression of this bifunctional enzyme-TPSP converted glucose to trehalose. The result suggested that TPSP from C. hutchinsonji has been successfully expressed in E. ccoi. High amount of extracellular trehalose generated from glucose by whole-cell catalysis and After optimization, the production of trehalose in shake flasks was improved to 1.2 g/L and the relative conversion rate reached 21%. The production in bioreactor reached 13.3 g/L and the relative conversion rate reached 48.6%. It is the first time to realize the functional expression of the bifunctional enzyme-TPSP of C. hutchinsonii in E. coli and achieved the conversion form glucose to trehalose. This study laid a foundation for industrial large-scale production of trehalose.
Bioreactors ; Catalysis ; Escherichia coli ; genetics ; Glucose ; Glucosyltransferases ; Industrial Microbiology ; Organisms, Genetically Modified ; Trehalose ; biosynthesis

We optimized the medium for recombinant dextransucrase expression in engineering strain Escherichia coli BL21 (DE3)/pET28-dexYG by an Orthogonal experiment. After the medium had been decided, we studied the effect of temperature, sucrose concentration and pH value on the yield. The results indicated that optimal conditions were adding IPTG of 0.25 mmol/L when OD600 reached 2.0 and cultivation lasted for 4 h at 25 degrees C. Under the selected medium and these conditions, the dextransucrase activity expressed by the engineering strain was high activity. Maximal activity reached 110.16 U/mL sucrose concentration effects the dextran yield grately. The results for dextransucrase expression would provide foundation for industrial application of dextransucrase.
Culture Media ; Culture Techniques ; methods ; Dextrans ; biosynthesis ; Escherichia coli ; genetics ; growth & development ; metabolism ; Glucosyltransferases ; biosynthesis ; genetics ; Recombinant Proteins ; biosynthesis ; genetics ; Sucrose ; metabolism

Sucrose phosphorylase (EC 2.4.1.7, Sucrose phosphorylase, SPase) can be produced by recombinant strain Escherichia coli Rosetta(DE3)/Pet-SPase. Crude enzyme was obtained from the cells by the high pressure disruption and centrifugation. Sucrose phosphorylase was purified by Ni-NTA affinity column chromatography and desalted by ultrafiltration. The specific enzyme activity was 1.1-fold higher than that of the crude enzyme, and recovery rate was 82.7%. The purified recombinant SPase had a band of 59 kDa on SDS-PAGE. Thermostability of the enzyme was shown at temperatures up to 37 degrees C, and pH stability between pH 6.0 and 6.7. The optimum temperature and pH were 37 degrees C and 6.7, respectively. The K(m) of SPase for sucrose was 7.3 mmol/L, and Vmax was 0.2 micromol/(min x mg). Besides, alpha-arbutin was synthesized from sucrose and hydroquinone by transglucosylation with recombinant SPase. The optimal conditions for synthesis of alpha-arbutin were 200 U/mL of recombinant SPase, 20% of sucrose, and 1.6% hydroquinone at pH 6-6.5 and 25 degrees C for 21 h. Under these conditions, alpha-arbutin was obtained with a 78.3% molar yield with respect to hydroquinone, and the concentration of alpha-arbutin was about 31 g/L.
Arbutin ; biosynthesis ; Catalysis ; Enzyme Stability ; Escherichia coli ; enzymology ; genetics ; Glucosyltransferases ; biosynthesis ; genetics ; metabolism ; Hydroquinones ; metabolism ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism ; Sucrose ; metabolism

To enhance the thermostability and storage stability of alpha-cyclodextrin glycosyltransferase (a-CGTase), we added specific chemical additives into the preparation of alpha-CGTase, and studied the effect of additives on the storage stability of alpha-CGTase at different temperatures. Then we measured the protein structure of CGTase in the far UV (200-250 nm) and near UV (250-320 nm) ranges respectively by Circular dichroism (CD) spectra under high temperature and analyzed the relationship between thermostability and protein structure. The results indicated that the addition of selected additives (gelatin, glycerin, CaCl2 and PEG400) enhanced the thermostability of alpha-CGTase dramatically. After 45 days, the preparation of alpha-CGTase still had 100% of the enzyme activity with different additives superimposed at the optimum concentration at 40 degrees C. The CD spectra of alpha-CGTase showed that glycerin could protect the secondary and the tertiary structure of the CGTase under high temperature and therefore the enzyme maintained its high activity. Chemical additives can improve the stability of alpha-CGTase significantly and they preserve the enzyme activity by protecting its secondary structure.
Enzyme Stability ; drug effects ; Escherichia coli ; genetics ; metabolism ; Glucosyltransferases ; biosynthesis ; chemistry ; genetics ; Glycerol ; chemistry ; Paenibacillus ; enzymology ; Recombinant Proteins ; biosynthesis ; chemistry ; genetics

OBJECTIVEClone of sucrose synthase of Dendribium officinale and expression analysis, to provide the theory basis for research the relationship between polysaccharide synthesis of D. officinale and sucrose synthase activity.

METHODAccording to homologous sequence of sucrose synthase gene on GenBank, application the technology of RT-PCR and RACE, clone the full length of D. officinale. Target gene amplified with T vector was transformed into competent E. coli. BL21, IPTG induced expression, SDS-PAGE analysis.

RESULTA full length cDNA encoding sucrose synthase was isolated from the D. officinale, named DOSS1, the GenBank accession number is HQ856835, the cDNA is 2781 bp in length containing an open reading frame of 2424 bp encoding 807 amino acids with a predicted molecular mass of 92.3 x 10(3), the deduced amino acid sequence of D. officinale sucrose synthase shares 95% identity with Mokara yellow (AF530568); shares 90% identity with Oncidium goldiana (AF530567); shares more than 80% with other monocotyledonous plants.

CONCLUSIONCloned the sucrose synthase gene and induced an obvious band successfully.

3' Untranslated Regions ; genetics ; 5' Untranslated Regions ; genetics ; Cloning, Molecular ; Dendrobium ; enzymology ; genetics ; metabolism ; Escherichia coli ; genetics ; Gene Expression Regulation, Plant ; Glucosyltransferases ; genetics ; metabolism ; Phylogeny ; Polysaccharides ; biosynthesis

OBJECTIVETo study the expression and significance of GCS gene in human pancreatic cancer cell line SW1990 and its drug-resistant sublines.

METHODSSW1990 and its drug-resistant sublines, SW1990/FU, SW1990/ADM and SW1990/GEM were cultured in vitro. CCK-8 (Cell Counting kit-8) was used to detect the drug resistance of the sublines. Relative quantitation of GCS mRNA expression was evaluated by real-time PCR and Western blot was adopted to evaluate the expression of GCS protein.

RESULTSThe drug resistance indexes of SW1990/FU, SW1990/ADM and SW1990/GEM were 339.7, 11.9 and 56.6, respectively. The GCS mRNA and protein were expressed in all SW1990 and its drug-resistant sublines. There was a higher expression of GCS mRNA in all the sublines and a significant difference of GCS protein expression was detected in SW1990/ADM and SW1990/GEM compared with SW1990.

CONCLUSIONSGCS gene is expressed in SW1990 and its drug-resistance sublines. The high expression of GCS protein in SW1990/ADM and SW1990/GEM might be one reason of resistance to ADM and GEM in the sublines.

Cell Line, Tumor ; Drug Resistance, Neoplasm ; genetics ; Gene Expression ; Glucosyltransferases ; biosynthesis ; genetics ; Humans ; Immunoblotting ; Pancreatic Neoplasms ; enzymology ; genetics ; pathology ; RNA, Messenger ; genetics ; Reverse Transcriptase Polymerase Chain Reaction

Improving stress tolerance of the microbial producers is of great importance for the process economy and efficiency of bioenergy production. Key genes influencing ethanol tolerance of brewing yeast can be revealed by studies on the molecular mechanisms which can lead to the further metabolic engineering manipulations for the improvement of ethanol tolerance and ethanol productivity. Trahalose shows protective effect on the cell viability of yeast against multiple environmental stress factors, however, further research is needed for the exploration of the underlying molecular mechanisms. In this study, the promoter region of the trehalose-6-phosphate synthase gene TPS1 was cloned from the self-flocculating yeast Saccharomyces cerevisiae flo, and a reporter plasmid based on the expression vector pYES2.0 on which the green fluorescence protein EGFP was directed by the TPS1 promoter was constructed and transformed to industrial yeast strain Saccharomyces cerevisiae ATCC4126. Analysis of the EGFP expression of the yeast transformants in presence of 7% and 10% ethanol revealed that the P(TPS1) activity was strongly induced by 7% ethanol, showing specific response to ethanol stress. The results of this study indicate that trehalose biosynthesis in self-flocculating yeast is a protective response against ethanol stress.
Base Sequence ; Cloning, Molecular ; Ethanol ; metabolism ; pharmacology ; Glucosyltransferases ; biosynthesis ; genetics ; Molecular Sequence Data ; Promoter Regions, Genetic ; genetics ; Saccharomyces cerevisiae ; enzymology ; genetics ; metabolism ; Stress, Physiological ; physiology

Acanthamoeba cysts are resistant to unfavorable physiological conditions and various disinfectants. Acanthamoeba cysts have 2 walls containing various sugar moieties, and in particular, one third of the inner wall is composed of cellulose. In this study, it has been shown that down-regulation of cellulose synthase by small interfering RNA (siRNA) significantly inhibits the formation of mature Acanthamoeba castellanii cysts. Calcofluor white staining and transmission electron microscopy revealed that siRNA transfected amoeba failed to form an inner wall during encystation and thus are likely to be more vulnerable. In addition, the expression of xylose isomerase, which is involved in cyst wall formation, was not altered in cellulose synthase down-regulated amoeba, indicating that cellulose synthase is a crucial factor for inner wall formation by Acanthamoeba during encystation.
Acanthamoeba castellanii/*enzymology/genetics/metabolism ; Aldose-Ketose Isomerases/*biosynthesis ; Amebiasis/*pathology ; Benzenesulfonates ; Cell Wall/chemistry/genetics/*metabolism ; Cellulose/biosynthesis ; Down-Regulation ; Encephalitis/parasitology ; Glucosyltransferases/*biosynthesis/genetics ; Keratitis/parasitology ; Microscopy, Electron, Transmission ; RNA Interference ; RNA, Small Interfering