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1.
A strain that exhibited intracellular proline-specific aminopeptidase (PAP) activity was isolated from soy sauce koji and identified as Aspergillus oryzae JN-412. The gene coding PAP was cloned and efficiently expressed in Escherichia coli BL21 in a biologically active form. The highest specific activity reached 52.28 U mg?1 at optimum cultivation conditions. The recombinant enzyme was purified 3.3-fold to homogeneity with a recovery of 36.7 % from cell-free extract using Ni-affinity column chromatography. It appeared as a single protein band on SDS-PAGE with molecular mass of approximately 50 kDa. The purified enzyme exhibited the highest activity at 60 °C and pH 7.5. The enzyme activity was inhibited by PMSF and ions like Zn2+ and Cu2+. DTT, β-mercaptoethanol, EDTA, and ions like Co2+, Mg2+, Mn2+, and Ca2+ had no influence on enzyme activity, whereas Ni2+ enhanced the enzyme activity. By using collagen as a substrate, the purified recombinant prolyl aminopeptidase contributed to the hydrolysis of collagen when used in combination with neutral protease, and free amino acids in collagen hydrolysates was significantly increased.  相似文献   

2.
An endo-β-1,4-xylanase-encoding gene, xyn11NX, was cloned from Nesterenkonia xinjiangensis CCTCC AA001025 and expressed in Escherichia coli. The gene encoded a 192-amino acid polypeptide and a putative 50-amino acid signal peptide. The deduced amino acid sequence exhibited a high degree of similarity with the xylanases from Streptomyces thermocyaneoviolaceus (68%) and Thermobifida fusca (66%) belonging to glycoside hydrolase family 11. After purification to homogeneity, the recombinant Xyn11NX exhibited optimal activity at pH 7.0 and 55 °C and remained stable at weakly acidic to alkaline pH (pH 5.0–11.0). The enzyme was thermostable, retaining more than 80% of the initial activity after incubation at 60 °C for 1 h and more than 40% of the activity at 90 °C for 15 min. The K m and V max values for oat spelt xylan and birchwood xylan were 16.08 mg ml?1 and 45.66 μmol min?1 mg?1 and 9.22 mg ml?1 and 16.05 μmol min?1 mg?1, respectively. The predominant hydrolysis products were xylobiose and xylotriose when using oat spelt xylan or birchwood xylan as substrate.  相似文献   

3.
A novel β-1,3-glucanase gene, designated Ccglu17A, was cloned from the biological control fungus Chaetomium cupreum Ame. Its 1626-bp open reading frame encoded 541 amino acids. The corresponding amino acid sequence showed highest identity (67 %) with a glycoside hydrolase family 17 β-1,3-glucanase from Chaetomium globosum. The recombinant protein Ccglu17A was successfully expressed in Pichia pastoris, and the enzyme was purified to homogeneity with 10.1-fold purification and 47.8 % recovery yield. The protein’s molecular mass was approximately 65 kDa, and its maximum activity appeared at pH 5.0 and temperature 45 °C. Heavy metal ions Fe2+, Mn2+, Cu2+, Co2+, Ag+, and Hg2+ had inhibitory effects on Ccglu17A, but Ba2+ promoted the enzyme’s activity. Ccglu17A exhibited high substrate specificity, almost exclusively catalyzing β-1,3-glycosidic bond cleavage in various polysaccharoses to liberate glucose. The enzyme had a Km of 2.84 mg/mL and Vmax of 10.7 μmol glucose/min/mg protein for laminarin degradation under optimal conditions. Ccglu17A was an exoglucanase with transglycosylation activity based on its hydrolytic properties. It showed potential antifungal activity with a degradative effect on cell walls and inhibitory action against the germination of pathogenic fungus. In conclusion, Ccglu17A is the first functional exo-1,3-β-glucanase to be identified from C. cupreum and has potential applicability in industry and agriculture.  相似文献   

4.
The enzyme from halophilic microorganisms often has unique properties such as organic-solvent-tolerance. In this study, a novel organic-solvent-tolerant α-amylase gene was cloned from the mild halophile Exiguobacterium sp. DAU5. The open reading frame (ORF) of the enzyme consisted of 1,545 bp and encoded 514 amino acids, the primary sequence revealed that it belongs to the glycoside hydrolase (GH) family 13. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed an AmyH monomer of 57 kDa. The enzyme exhibited maximal activity at 40 °C in pH?8.5 glycine–NaOH buffer, and the activity was strongly inhibited by Zn2+, Cu2+, and Fe2+. The α-amylase AmyH exhibited high hydrolysis activity toward soluble starch, and the major hydrolysis products were maltose, maltotriose, and maltopentaose; the AmyH could not efficiently hydrolyze oligosaccharides smaller than maltoheptaose, nor could it act on the β-1,4 or α-1,6 glucosidic bonds in xylan or pullulan, respectively. In addition, the α-amylase exhibited better tolerance to organic solvents, as it was stable in the presence of dimethylsulfoxide (DMSO), methanol, ethanol, and acetone. Base on all of these results, the enzyme could be useful for practical application in the bakery industry and in biotechnological processes that occur in the presence of organic solvents.  相似文献   

5.
A gene encoding methylglyoxal synthase from Thermus sp. GH5 (TMGS) was cloned, sequenced, overexpressed, and purified by Q-Sepharose. The TMGS gene was composed of 399 bp which encoded a polypeptide of 132 amino acids with a molecular mass of 14.3 kDa. The K m and k cat values of TMGS were 0.56 mM and 325 (s?1), respectively. The enzyme exhibited its optimum activity at pH?6 and 75?°C. Comparing the amino acid sequences and Hill coefficients of Escherichia coli MGS and TMGS revealed that the loss of Arg 150 in TMGS has caused a decrease in the cooperativity between the enzyme subunits in the presence of phosphate as an allosteric inhibitor. Gel filtration experiments showed that TMGS is a hexameric enzyme, and its quaternary structure did not change in the presence of phosphate.  相似文献   

6.
Humicola insolens produced a new β-glucosidase (BglHi2) under solid-state fermentation. The purified enzyme showed apparent molecular masses of 116 kDa (sodium dodecyl sulfate–polyacrylamide gel electrophoresis) and 404 kDa (gel-filtration), suggesting that it is a homotetramer. Mass spectrometry analysis showed amino acid sequence similarity with a β-glucosidase from Chaetomium thermophilum. Optima of pH and temperature were 5.0 and 65 °C, respectively, and the enzyme was stable for 60 min at 50 °C, maintaining 71 % residual activity after 60 min at 55 °C. BglHi2 hydrolyzed p-nitrophenyl-β-d-glucopyranoside and cellobiose. Cellobiose hydrolysis occurred with high apparent affinity (K M?=?0.24?±?0.01 mmol L?1) and catalytic efficiency (k cat/K M?=?1,304.92?±?53.32 L mmol?1 s?1). The activity was insensitive to Fe+3, Cr+2, Mn+2, Co+2, and Ni2+, and 50–60 % residual activities were retained in the presence of Pb2+, Hg2+, and Cu2+. Mixtures of pure BglHi2 or H. insolens crude extract (CE) with crude extracts from Trichoderma reesei fully hydrolyzed Whatman no. 1 paper. Mixtures of H. insolens CE with T. reesei CE or Celluclast 1.5 L fully hydrolyzed untreated printed office paper, napkin, and magazine papers after 24–48 h, and untreated cardboard was hydrolyzed by a H. insolens CE/T. reesei CE mixture with 100 % glucose yield. Data revealed the good potential of BglHi2 for the hydrolysis of waste papers, promising feedstocks for cellulosic ethanol production.  相似文献   

7.
Aminopeptidases catalyze the cleavage of specific amino acids from the amino terminus of protein or peptide substrates. A proline-specific aminopeptidase was purified to homogeneity from the culture-free extract of Streptomyces lavendulae ATCC 14162 in sequential steps comprising ammonium sulfate precipitation, ultra-filtration, and column chromatography on Q-sepharose and Sephadex G-100. The purified protein showed approximately 60 kDa in SDS-PAGE and was optimally active at pH 6.5 and 40 °C. Kinetic studies showed a K m and V max of 0.23 mM and 0.087 μmol/min, respectively, using Pro-p-NA, the substrate with maximum specificity. Enzyme activity was inhibited by PMSF and ions like Zn2+, Co2+, and Ni2+. However, unlike other aminopeptidases, the activity was enhanced in the presence of DTT, 1,10-phenanthroline, EDTA, amastatin, and bestatin. Ions like Ca2+, Mg2+, and Mn2+ also enhanced the activity.  相似文献   

8.
Based on thermal asymmetric interlaced polymerase chain reaction, the arpde gene encoding a cyclic nucleotide-specific phosphodiesterase was cloned from Arthrobacter sp. CGMCC 3584 for the first time. The 930-bp region encoded a 309-amino-acid protein with a molecular weight of 33.6 kDa. The recombinant ArPDE was able to hydrolyze 3′,5′-cAMP, 3′,5′-cGMP, and 2′,3′-cAMP. The K m values of ArPDE for 3′,5′-cAMP and 3′,5′-cGMP were 6.82 and 12.82 mM, respectively. ArPDE was thermostable and displayed optimal activity at 45 °C and pH 7.5. The enzyme did not require any metal cofactors, although its activity was stimulated by 2 mM Co2+ and inhibited by Zn2+. Nucleotides, reducing agents, and sulfhydryl reagents had different inhibitory effects on the activity of ArPDE. NaF, the actual compound used to improve the industrial yield of cAMP, exhibited 62 % inhibitions at concentrations of 10 mM.  相似文献   

9.
Endonuclease I is a widely distributed periplasmic or extracellular enzyme. A method for the high-level production of recombinant AsEndI (endonuclease I from Aliivibrio salmonicida) in Escherichia coli with secretion expression is investigated. The coding sequence of AsEndI gene was assembled according to the E. coli codon usage bias, and AsEndI was expressed in the periplasm of E. coli TOP10 with a C-terminal 6× His-tagged fusion. The recombinant AsEndI (His-AsEndI) was purified by Ni-NTA resin with a yield of 1.29?×?107 U from 1-L LB medium. His-AsEndI could be classified into Ca2+/Mg2+-dependent nucleases and showed highest nuclease activity to dsDNA at pH 8.0 and 37 °C. His-AsEndI is highly active in a broad range of salt concentration range up to 1.0 M with optimal NaCl concentration at 0.4 M. His-AsEndI can effectively remove DNA contamination in RNA sample or in PCR reagents to the level that cannot be detected by highly sensitive nested PCR and without adverse effects on the subsequent PCR reaction. His-AsEndI can remove DNA contamination at high salt conditions, especially for the DNA that may be shielded by DNA-binding protein at low salt conditions.  相似文献   

10.
Tripeptidyl peptidase (TPP) is an exopeptidase that sequentially hydrolyzes tripeptides from the N-terminus of oligopeptides or polypeptides. We performed screening for isolating novel TPP-producing microorganisms from soil samples. TPP activity was observed in the culture supernatant of Streptomyces herbaricolor TY-21 by using Ala-Ala-Phe-p-nitroanilide (pNA) as the substrate. TPP from the culture supernatant was purified to approximately 790-fold. It was shown to cleave oxidized insulin B-chain, thereby with releasing tripeptide units, but not the N-terminal-protected peptide, Cbz-Ala-Ala-Phe-pNA. The TPP gene, designated tpp, was isolated from a partial genomic DNA library of S. herbaricolor TY-21. The TPP gene consisted of 1488 bp, and encoded a 133-amino acid pre-pro-peptide and a 362-amino acid mature enzyme containing conserved amino acid residues (Asp-36, His-77, and Ser-282) similar to the catalytic residues in subtilisin. TY-21 TPP belonged to the peptidase S8A family in the MEROPS database. The mature TY-21 TPP showed approximately 49% identity with tripeptidyl peptidase subtilisin-like (TPP S) from Streptomyces lividans strain 66.  相似文献   

11.
A yeast isolate able to produce high levels of extracellular ??-amylase was selected from a collection of 385 yeasts and identified as Wickerhamia sp. by the sequence of the D1/D2 domain of the 26?S rDNA gene. Part of the nucleotide sequence of the amy1-W gene was cloned, and a sequence of 191 amino acids deduced from this gene was analyzed. The peptide contains three characteristic well-conserved regions in the active sites of ??-amylases (EC 3.2.1.1). The enzyme was purified and in situ activity showed only one band with amylolytic activity. The molecular mass of the ??-amylase was estimated at 54?kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Enzymatic activity on soluble starch as substrate was optimal at pH 5?C6 and 50 °C. This thermostable enzyme was inhibited by EDTA?CNa2 and 1,10-phenanthroline; the activity of the dialyzed enzyme was reactivated with Ca2+ and Mg2+ cations, which indicates that the ??-amylase is a metalloenzyme. ??-Amylase production was induced by starch and maltose and repressed by glucose. The high yield and productivity found in this work makes this Wickerhamia sp. strain a promising candidate for the biotechnological production of ??-amylase.  相似文献   

12.
An inulinase-producing strain, Paenibacillus polymyxa ZJ-9, was isolated from natural sources to produce R,R-2,3-butanediol via one-step fermentation of raw inulin extracted from Jerusalem artichoke tubers. The inulinase gene from P. polymyxa ZJ-9 was cloned and overexpressed in Escherichia coli BL21 (DE3), and the purified recombinant inulinase was estimated to be approximately 56 kDa by both sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) and gel filtration chromatography. This result suggests that the active form of the inulinase is probably a monomer. Terminal hydrolysis fructose units from the inulin indicate that enzymes are exo-inulinase. The purified recombinant enzyme showed maximum activity at 25 °C and pH 6.0, which indicate its extreme suitability for industrial applications. Zn2+, Fe2+, and Mg2+ stimulated the activity of the purified enzyme, whereas Co2+, Cu2+, and Ni2+ inhibited enzyme activity. The K m and V max values for inulin hydrolysis were 1.72 mM and 21.69 μmol min?1 mg?1 protein, respectively. The same parameters toward sucrose were 41.09 mM and 78.7 μmol min?1 mg?1 protein, respectively. Considering its substrate specificity and other enzymatic characteristics, we believe that this inulinase gene from P. polymyxa ZJ-9 could be transformed into other special bacterial strains to allow inulin conversion to other biochemicals and bioenergy through one-step fermentation.  相似文献   

13.
Purification, characterization, gene cloning, and heterologous expression in Escherichia coli of a thermostable β-1,3-1,4-glucanase from Bacillus altitudinis YC-9 have been investigated in this paper. The donor strain B. altitudinis YC-9 was isolated from spring silt. The native enzyme was purified by ammonium sulfate precipitation, diethylaminoethyl-cellulose anion exchange chromatography, and Sephadex G-100 gel filtration. The purified β-1,3-1,4-glucanase was observed to be stable at 60 °C and retain more than 90 % activity when incubated for 2 h at 60 °C and remain about 75 % and 44 % activity after incubating at 70 °C and 80 °C for 10 min, respectively. Acidity and temperature optimal for this enzyme was pH 6 and 65 °C. The open reading frame of the enzyme gene was measured to be 732 bp encoding 243 amino acids, with a predicted molecular weight of 27.47 kDa. The gene sequence of β-1,3-1,4-glucanase showed a homology of 98 % with that of Bacillus licheniformis. After being expressed in E. coli BL21, active recombinant enzyme was detected both in the supernatants of the culture and the cell lysate, with the activity of 102.7 and 216.7 U/mL, respectively. The supernatants of the culture were used to purify the recombinant enzyme. The purified recombinant enzyme was characterized to show almost the same properties to the wild enzyme, except that the specific activity of the recombinant enzyme reached 5392.7 U/mg, which was higher than those ever reported β-1,3-1,4-glucanase from Bacillus strains. The thermal stability and high activity make this enzyme broad prospect for industry application. This is the first report on β-1,3-1,4-glucanase produced by B. altitudinis.  相似文献   

14.
15.
A novel halohydrin dehalogenase (HHDH), catalyzing the transformation of 1,3-dichloro-2-propanol (1,3-DCP) to epichlorohydrin (ECH), was purified from Agromyces mediolanus ZJB120203. The molecular mass of the enzyme was estimated to be 28 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A 735-bp nucleotide fragment was obtained based on the N-terminal and internal amino acid sequences of the purified HHDH. The gene codes a protein sequence with 244 amino acid residues, and the protein sequence shows high similarity to Hhe AAD2 (HHDH from Arthrobacter sp. AD2), defined as Hhe AAm, which is the seventh reported HHDH. Expression of Hhe AAm was carried out in Escherichia coli and purification was performed by nickel-affinity chromatography. The recombinant HheAAm possessed an optimal pH of 8.5 and an optimal temperature of 50 °C and manifested a K m of 4.58 mM and a V max of 3.84 μmol/min/mg. The activity of Hhe AAm was not significantly affected by metal ions such as Zn2+, Ca2+, Cu2+, and EDTA, but was strongly inhibited by Hg2+ and Ag+. In particular, the Hhe AAm exhibits an enantioselectivity for the conversion of prochiral 1,3-DCP to (S)-ECH. The applications of the Hhe AAm as a catalyst for asymmetric synthesis are promising.  相似文献   

16.
Five hundred ninety-seven bacterial isolates from Turkish hot spring water sources were screened for their ability to produce extracellular α-amylase. Among them, a high enzyme-producing Bacillus subtilis isolate, A28, was selected, and its α-amylase gene was cloned and expressed in Escherichia coli by a ligase-independent method. α-Amylase from the recombinant strain was purified to homogeneity by Q-Sepharose anion exchange and Sephacryl S-100 gel filtration chromatographies. The final yield of the enzyme was about 22.5 % of the initial activity, with a 16.4-fold increase in specific activity compared with the culture lysate. The optimum temperature and pH of the enzyme were 70 °C and 6.0, respectively. The enzyme was highly active at acidic-neutral pH range of 4.5–7.0. The amy28 α-amylase retained 100 % of its activity after incubation at 50 °C for 90 min. Co+2, Cu2+, Fe2+, Fe3+, Ni+2, and Zn+2 caused significant inhibition in enzyme activity, which was not affected by Na+, Mg2+, Li+, and Ba2+. The activity was inhibited about 70 % upon treatment of the enzyme with 10 mM ethylenediaminetetraacetic acid. However, Ca2+ ions known as high temperature stabilizer for other amylases did not stimulate the activity of the enzyme. Due to pH stability and thermostability of the recombinant amylase, this enzyme may be suitable in starch processing, brewing, and food industries.  相似文献   

17.
A novel cold-adapted lipase (designated as LipYY31) was obtained from a psychrotrophic Pseudomonas sp. YY31. The strain YY31 was gram-negative, rod shaped, motile by means of one polar flagellum, and exhibited chemotaxis toward oil droplets under a microscope. The strain displayed remarkable degradation of edible oil and fat even at 5 °C. The LipYY31 DNA fragment contains an open reading frame of 1,410 bp which encoded a protein of 470 amino acids with an estimated molecular mass of 49,584 Da. LipYY31 showed high sequence similarity to those of subfamily Ι.3 lipase and had a conserved GXSXG motif around the catalytic Ser residue. Its optimal temperature was 25–30 °C, and it retained 20–40 % of its activity at 0–5 °C. The optimal pH value was 8.0. The activity was strongly inhibited by Cd2+, Zn2+, EDTA and was highly dependent on Ca2+. Tricaprin and p-nitrophenyl caprate were the most favorable substrates among the triglycerides and p-nitrophenyl esters, respectively. LipYY31 also had high activity towards natural substrates including edible vegetable oils and animal fat. Furthermore, LipYY31 was very active and stable in the presence of several detergents and organic solvents. In particular, the lipase exhibited high stability against organic solvents such as methanol, ethanol, and isopropanol.  相似文献   

18.
A monomeric feruloyl esterase (FAE) with a molecular mass of 62 kDa was acquired from fresh fruiting bodies of the edible mushroom Russula virescens. The isolation procedure involved ion exchange chromatography on CM-cellulose, Q-Sepharose, and SP-Sepharose and finally fast protein liquid chromatography–gel filtration on Superdex 75. Two amino acid sequences were obtained after tryptic digestion, and they both showed some homology with the esterase of some fungi. Maximal activity was observed at pH 5.0 and at 50 °C. The enzyme displayed relatively high thermostability as evidenced by over 70 % residual activity at 70 °C and about 34 % residual activity at 80 °C. The K m and V max for this enzyme on methyl ferulate were 0.19 mM and 1.65 U/mg proteins, respectively. The purified FAE prefers methyl ferulate over methyl caffeate and is least active on methyl p-coumarate. The FAE activity was not significantly affected by the presence of cations such as Mn2+, Ca2+, Cd2+, Zn2+, Mg2+, Cu2+, and K+ ions but inhibited by Al3+, Hg2+, Fe2+, and Pb2+ ions at a tested concentration of 2. 5 mM.  相似文献   

19.
The present investigation highlights the optimal conditions for production of a non-toxic, bi-functional fibrinolytic enzyme xylarinase produced by endophytic fungus Xylaria curta by solid substrate fermentation using rice chaff medium. The purified enzyme is a monomeric protein with a molecular mass of ~33 kDa. The enzyme exhibits cleavage of Aα and Bβ chains of fibrin(ogen) and has no effect on γ chain. The optimal fibrinolytic activity of the enzyme was observed at 35 °C and pH 8. The fibrinolytic activity was enhanced in the presence of Ca2+, whereas it was completely inhibited in the presence of Fe2+ and Zn2+ ions and inhibitors like EDTA and EGTA suggesting it to be a metalloprotease. The K m and V max of the enzyme for azocasein were 326 μM and 0.13 μM min?1. The N-terminal sequence of the enzyme (SNGPLPGGVVWAG) was same when compared to xylarinase isolated from culture broth of X. curta. Thus, xylarinase could be exploited as a potent clot busting enzyme which could be produced on large scale using solid substrate fermentation.  相似文献   

20.
Amylases are important industrial enzymes that have been applied widely in the food, detergent, and pulp industries and fermentation processes. In the present study, a gene encoding an alpha-amylase from the genomic DNA library of Paenibacillus sp. was identified and characterized. The amylase gene designated amy1 was shown to consist of 1,980 bp and shared sequence identity towards α-amylase genes from other Bacillus sp. The deduced amino acid sequence for Amy1 indicated 80 % sequence identity with other Bacillus strains. Heterologous expression of recombinant Amy1 in Escherichia coli BL21(DE3) facilitated the recovery of this protein in soluble form. Enzyme kinetic data revealed Amy1 to have a K m of 23.83 mg/mL and K cat of 48.74 min?1 and K cat /K m of 2 min?1 mg?1 mL?1 for starch. The activity of this protein was found to be enhanced by Mn2+, and furthermore, Amy1 remained active at a broad pH range (4–10) and temperature (30–90 °C). The ability of Amy1 to act on food waste under broad temperature and pH conditions, together with its ability to produce simple sugars, shows many advantages for further application in the food industry.  相似文献   

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