共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Vidyasagar S. Prakash S. K. Jayalakshmi K. Sreeramulu 《World journal of microbiology & biotechnology》2007,23(5):655-662
An extremely halophilic Chromohalobacter sp. TVSP101 was isolated from solar salterns and screened for the production of extracellular halothermophilic protease.
Identification of the bacterium was done based upon biochemical tests and the 16S rRNA sequence. The partially purified enzyme
displayed maximum activity at pH 8 and required 4.5 M of NaCl for optimum proteolytic activity. In addition, this enzyme was
thermophilic and active in broad range of temperature 60–80°C with 80°C as optimum. The Chromohalobacter sp. required 4 M NaCl for its optimum growth and protease secretion and no growth was observed below 1 M of NaCl. The initial
pH of the medium for growth and enzyme production was in the range 7.0–8.0 with optimum at pH 7.2. Various cations at 1 mM
concentration in the growth medium had no significant effect in enhancing the growth and enzyme production but 0.5 M MgCl2 concentration enhanced enzyme production. Casein or skim milk powder 1% (w/v) along with 1% peptone proved to be the best
nitrogen sources for maximum biomass and enzyme production. The carbon sources glucose and glycerol repressed the protease
secretion. Immobilization of whole cells in absence of NaCl proved to be useful for continuous production of halophilic protease. 相似文献
2.
Dastager SG Dayanand A Li WJ Kim CJ Lee JC Park DJ Tian XP Raziuddin QS 《Current microbiology》2008,57(6):638-642
Multiple proteases were produced and partially purified from an alkali-thermotolerant novel species of Streptomyces (i.e.,
Streptomyces gulbargensis DAS 131) after 48 h of growth at 45°C. The enzyme preparation exhibited activity over a broad range of pH (4–12) and temperature
(27–55°C). Optimum activity was observed at a pH of 9.0 and a temperature of 45°C. Starch and protease peptone was found to
be a good source of carbon and nitrogen to enhance the enzyme activity. Two active zones in the range of 19 to 35 kDa were
detected on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). 相似文献
3.
Nack-Shick Choi Jae Jun Song Dong-Min Chung Young Jae Kim Pil Jae Maeng Seung-Ho Kim 《Journal of industrial microbiology & biotechnology》2009,36(3):417-426
A novel fibrinolytic enzyme (AJ) was purified from Staphylococcus sp. strain AJ screened from Korean salt-fermented Anchovy-jeot. Relative molecular weight of AJ was determined as 26 kDa by using SDS-PAGE and fibrin zymography. Based on a 2D gel, AJ
was found to consist of three active isoforms (pI 5.5–6.0) with the same N-terminal amino acid sequence. AJ exhibited optimum pH and temperature at 2.5–3.0 and 85°C, respectively.
AJ kept 85% of the initial activity after heating at 100°C for 20 min on the zymogram gel. The Michaelis constant (K
m) and K
cat values of AJ towards α-casein were 0.38 mM and 19.73 s−1, respectively. AJ cleaved the Aα-chain of fibrinogen but did not affect the Bβ- and γ-chains, indicating that it is an α-fibrinogenase.
The fibrinolytic activity was inhibited by diisopropyl fluorophosphate, indicating AJ is a serine protease. Interestingly,
AJ was very stable at acidic condition, SDS, and heat (100°C), whereas it was easily degraded at neutral and alkaline conditions.
In particular, AJ formed an active homo-dimer in the pH range from 7.0 to 8.0. To our knowledge, a similar combination of
acid and heat stability has not yet been reported for other fibrinolytic enzymes. 相似文献
4.
Dodia MS Rawal CM Bhimani HG Joshi RH Khare SK Singh SP 《Journal of industrial microbiology & biotechnology》2008,35(2):121-131
An alkaline protease secreting Haloalkaliphilic bacterium (Gene bank accession number EU118361) was isolated from the Saurashtra
Coast in Western India. The alkaline protease was purified by a single step chromatography on phenyl sepharose 6 FF with 28%
yield. The molecular mass was 40 kDa as judged by SDS-PAGE. The enzyme displayed catalysis and stability over pH 8–13, optimally
at 9–11. It was stable with 0–4 M NaCl and required 150 mM NaCl for optimum catalysis at 37 °C; however, the salt requirement
for optimal catalysis increased with temperature. While crude enzyme was active at 25–80 °C (optimum at 50 °C), the purified
enzyme had temperature optimum at 37 °C, which shifted to 80 °C in the presence of 2 M NaCl. The NaCl not only shifted the
temperature profile but also enhanced the substrate affinity of the enzyme as reflected by the increase in the catalytic constant
(K
cat). The enzyme was also calcium dependent and with 2 mM Ca+2, the activity reached to maximum at 50 °C. The crude enzyme was highly thermostable (37–90 °C); however, the purified enzyme
lost its stability above 50 °C and its half life was enhanced by 30 and sevenfold at 60 °C with 1 M NaCl and 50 mM Ca+2, respectively. The activity of the enzyme was inhibited by PMSF, indicating its serine type. While the activity was slightly
enhanced by Tween-80 (0.2%) and Triton X-100 (0.05%), it marginally decreased with SDS. In addition, the enzyme was highly
stable with oxidizing-reducing agents and commercial detergents and was affected by metal ions to varying extent. The study
assumes significance due to the enzyme stability under the dual extremities of pH and salt coupled with moderate thermal tolerance.
Besides, the facts emerged on the enzyme stability would add to the limited information on this enzyme from Haloalkaliphilic
bacteria. 相似文献
5.
Purification and characterization of a serine alkaline protease from Bacillus clausii GMBAE 42 总被引:1,自引:0,他引:1
Kazan D Denizci AA Oner MN Erarslan A 《Journal of industrial microbiology & biotechnology》2005,32(8):335-344
An extracellular serine alkaline protease of Bacillus clausii GMBAE 42 was produced in protein-rich medium in shake-flask cultures for 3 days at pH 10.5 and 37°C. Highest alkaline protease
activity was observed in the late stationary phase of cell cultivation. The enzyme was purified 16-fold from culture filtrate
by DEAE-cellulose chromatography followed by (NH4)2SO4 precipitation, with a yield of 58%. SDS-PAGE analysis revealed the molecular weight of the enzyme to be 26.50 kDa. The optimum
temperature for enzyme activity was 60°C; however, it is shifted to 70°C after addition of 5 mM Ca2+ ions. The enzyme was stable between 30 and 40°C for 2 h at pH 10.5; only 14% activity loss was observed at 50°C. The optimal
pH of the enzyme was 11.3. The enzyme was also stable in the pH 9.0–12.2 range for 24 h at 30°C; however, activity losses
of 38% and 76% were observed at pH values of 12.7 and 13.0, respectively. The activation energy of Hammarsten casein hydrolysis
by the purified enzyme was 10.59 kcal mol−1 (44.30 kJ mol−1). The enzyme was stable in the presence of the 1% (w/v) Tween-20, Tween-40,Tween-60, Tween-80, and 0.2% (w/v) SDS for 1 h
at 30°C and pH 10.5. Only 10% activity loss was observed with 1% sodium perborate under the same conditions. The enzyme was
not inhibited by iodoacetate, ethylacetimidate, phenylglyoxal, iodoacetimidate, n-ethylmaleimidate, n-bromosuccinimide, diethylpyrocarbonate or n-ethyl-5-phenyl-iso-xazolium-3′-sulfonate. Its complete inhibition by phenylmethanesulfonylfluoride and relatively high k
cat value for N-Suc-Ala-Ala-Pro-Phe-pNA hydrolysis indicates that the enzyme is a chymotrypsin-like serine protease. K
m and k
cat values were estimated at 0.655 μM N-Suc-Ala-Ala-Pro-Phe-pNA and 4.21×103 min−1, respectively. 相似文献
6.
I Saba PH Qazi SA Rather RA Dar QA Qadri N Ahmad S Johri SC Taneja S Shawl 《World journal of microbiology & biotechnology》2012,28(3):1071-1079
A Psychrotolerant alkaline protease producing bacterium IIIM-ST045 was isolated from a soil sample collected from the Thajiwas
glacier of Kashmir, India and identified as Stenotrophomonas sp. on the basis of its biochemical properties and 16S ribosomal gene sequencing. The strain could grow well within a temperature
range of 4–37°C however, showed optimum growth at 15°C. The strain was found to over-produce proteases when it was grown in
media containing lactose as carbon source (157.50 U mg−1). The maximum specific enzyme activity (398 U mg−1) was obtained using soya oil as nitrogen source, however, the inorganic nitrogen sources urea, ammonium chloride and ammonium
sulphate showed the lowest production of 38.9, 62.2 and 57.9 U mg−1. The enzyme was purified to 18.45 folds and the molecular weight of the partially purified protease was estimated to be ~55 kDa
by SDS-PAGE analysis. The protease activity increased as the increase in enzyme concentration while as the optimum enzyme
activity was found when casein (1% w/v) was used as substrate. The enzyme was highly active over a wide range of pH from 6.5
to 12.0 showing optimum activity at pH 10.0. The optimum temperature for the enzyme was 15°C. Proteolytic activity reduced
gradually with higher temperatures with a decrease of 56% at 40°C. The purified enzyme was checked for the removal of protein
containing tea stains using a silk cloth within a temperature range of 10–60°C. The best washing efficiency results obtained
at low temperatures indicate that the enzyme may be used for cold washing purposes of delicate fabrics that otherwise are
vulnerable to high temperatures. 相似文献
7.
Valeria Calandrelli Agata Gambacorta Ida Romano Vito Carratore Licia Lama 《World journal of microbiology & biotechnology》2008,24(10):2269-2275
A novel thermo-alkali-stable catalase–peroxidase from Oceanobacillus oncorhynchi subsp. incaldaniensis subsp. nov., strain 20AG, was purified and characterized. The protein purified from the cells resulted in 110-fold purification
with a specific activity of 35,000 U/mg. The enzyme consisted of four identical subunits of 72 kDa as determined by SDS-PAGE
and the total molecular mass measured by gel filtration was 280 kDa. The heme content was determined to be 1 heme per homodimer.
The enzyme showed a Soret peak at 406 nm in the oxidized form and was easily reduced by dithionite. The enzyme showed an appreciable
peroxidase activity in addition to high catalase activity. The behaviour of this heme-enzyme was typical of the class of prokaryotic
catalase–peroxidases, which are sensitive to cyanide and insensitive to the eukaryotic catalase inhibitor 3-amino-1,2,4-triazole.
The enzyme was active over a temperature range from 30 to 60°C and a pH range from 5 to 10, with an optimum pH about 9.0 and
an optimum temperature of 40°C. The enzyme was stable in the pH range of 5.0 to 10.0 after 1 h of treatment at 40°C. The enzyme
was stable for 24 h at 40°C with a half-life of 4 h 60°C. The enzyme had a K
m of 24 mM for hydrogen peroxide. The amino terminal amino acid sequence of the catalase–peroxidase from strain 20AG was SEKRKMTTAFGA
and it showed no homology with other catalases. 相似文献
8.
Koma D Yamanaka H Moriyoshi K Ohmoto T Sakai K 《Extremophiles : life under extreme conditions》2007,11(6):769-779
A novel extracellular serine protease derived from Thermoanaerobacter tengcongensis, designated tengconlysin, was successfully overexpressed in Escherichia coli as a soluble protein by recombination of an N-terminal Pel B leader sequence instead of the original presequence and C-terminal
6× histidine tags. The purified protein was activated by 0.1% sodium dodecyl sulfate (SDS) treatment but not by thermal treatment.
The molecular weight of tengconlysin estimated by SDS-polyacrylamide gel electrophoresis analysis and gel filtration chromatography
was 37.9 and 36.2 kDa, respectively, suggesting that the enzyme is monomeric. The N-terminal sequence of mature tengconlysin
was LDTAT, suggesting that it is a preproprotein containing a 29 amino acid presequence (predicted from the SigP program)
and a 117 amino acid prosequence in the N-terminus. The C-terminal putative propeptide (position 469–540 in the preproprotein)
did not inhibit the protease activity. The optimum temperature for tengconlysin activity was 90°C in the presence of 1 mM
calcium ions and the optimum pH ranged from 6.5 to 7.0. Activity inhibition studies suggest that the protease is a serine
protease. The protease was stable in 0.1% SDS and 1–4 M urea at 70°C in the presence of calcium ions and was activated by
the denaturing agents. 相似文献
9.
Canakci S Kacagan M Inan K Belduz AO Saha BC 《Applied microbiology and biotechnology》2008,81(1):61-68
The gene, AbfAC26Sari, encoding an α-l-arabinofuranosidase from Anoxybacillus kestanbolensis AC26Sari, was isolated, cloned, sequenced, and characterizated. On the basis of amino acid sequence similarities, this 57-kDa
enzyme could be assigned to family 51 of the glycosyl hydrolase classification system. Characterization of the purified recombinant
α-l-arabinofuranosidase produced in Escherichia coli BL21 revealed that it is active at a broad pH range (pH 4.5 to 9.0) and at a broad temperature range (45–85°C) and it has
an optimum pH of 5.5 and an optimum temperature of 65°C. Kinetic experiment at 65°C with p-nitrophenyl α-l-arabinofuranoside as a substrate gave a V
max and K
m values of 1,019 U/mg and 0.139 mM, respectively. The enzyme had no apparent requirement of metal ions for activity, and its
activity was strongly inhibited by 1 mM Cu2+ and Hg2+. The recombinant arabinofuranosidase released l-arabinose from arabinan, arabinoxylan, oat spelt xylan, arabinobiose, arabinotriose, arabinotetraose, and arabinopentaose.
Endoarabinanase activity was not detected. These findings suggest that AbfAC26Sari is an exo-acting enzyme. 相似文献
10.
Zhiyu Liu Dongxu Zhang Zhaozhe Hua Jianghua Li Guocheng Du Jian Chen 《Bioprocess and biosystems engineering》2010,33(5):639-646
Low-energy ion implantation was employed to breed laccase producing strain Paecilomyces sp. WSH-L07 and a mutant S152 that exhibited an activity of more than three times over the wild strain was obtained. The
optimum substrate of both the wild and mutant laccases was 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate), and followed
by guaiacol with optimal pH at 3.4 and 5.0, respectively, while the mutant laccase exhibited a broader active pH range. The
mutant laccase had a higher optimal catalytic temperature (60–65 °C) than the wild one (55 °C), and the wild laccase deactivated
rapidly when temperature increased above 55 °C. Furthermore, the mutant laccase was more stable under neutral and alkaline
conditions. A thermostability experiment revealed that the mutant laccase was superior to the wild laccase. Both laccases
were stable in the presence of metal ions, mildly inhibited by SDS (0.5 mM), EDTA (1 mM) and 1,4-dithiothreitol (0.5 mM),
and almost completely inhibited by 0.1 mM NaN3. 相似文献
11.
A chitosanase and a protease were purified from the culture supernatant of Serratia sp. TKU016 with shrimp shell as the sole carbon/nitrogen source. The molecular masses of the chitosanase and protease determined
by SDS–PAGE were approximately 65 and 53 kDa, respectively. The chitosanase was inhibited completely by Mn2+, but the protease was enhanced by all of tested divalent metals. The optimum pH, optimum temperature, pH stability, and thermal
stability of the chitosanase and protease were (pH 7, 50°C, pH 6–7, <50°C) and (pH 8–10, 40°C, pH 5–10, <50°C), respectively.
SDS (2 mM) had stimulatory effect on TKU016 protease activity. The result demonstrates that TKU016 protease is SDS-resistant
protease and probably has a rigid structure. Besides, TKU016 culture supernatant (2% SPP) incubated for 2 days has the highest
antioxidant activity, the DPPH scavenging ability was about 76%. With this method, we have shown that shrimp shell wastes
can be utilized and it’s effective in the production of enzymes, antioxidants, peptide and reducing sugar, facilitating its
potential use in biological applications and functional foods. 相似文献
12.
Giri SS Sukumaran V Sen SS Oviya M Banu BN Jena PK 《Journal of microbiology (Seoul, Korea)》2011,49(3):455-461
An extracellular detergent tolerant protease producing strain VSG-4 was isolated from tropical soil sample and identified
as Bacillus subtilis based on morphological, biochemical characteristics as well as 16S-rRNA gene sequencing. The VSG-4 protease was purified
to homogeneity using ammonium sulphate precipitation, dialysis and sephadex G-200 gel permeation chromatography with a 17.4
purification fold. The purified enzyme was active and stable over a broad range of pH (8.0–11.0, optimum at 9.0) and temperature
(40°C to 60°C, optimum at 50°C). The thermostability of the enzyme was significantly increased by the addition CaCl2. This enzyme was strongly inhibited by PMSF and DFP, suggesting that it belongs to the serine protease superfamily. The purified
VSG-4 alkaline protease showed remarkable stability in anionic (5 mM SDS) and ionic (1% Trion X-100 and 1% Tween 80) detergents.
It retained 97±2% and 83.6±1.1% of its initial activity after 1 h preincubation in the presence of 1 % H2O2 and 1 % sodium perborate, respectively. Furthermore, the purified enzyme showed excellent stability and compatibility with
some commercial laundry detergents besides its stain removal capacity. Considering these promising properties, VSG-4 protease
may find tremendous application in laundry detergent formulations. 相似文献
13.
Chellappan S Jasmin C Basheer SM Kishore A Elyas KK Bhat SG Chandrasekaran M 《Journal of industrial microbiology & biotechnology》2011,38(6):743-752
An alkaline protease from marine Engyodontium album was characterized for its physicochemical properties towards evaluation of its suitability for potential industrial applications.
Molecular mass of the enzyme by matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) analysis was calculated
as 28.6 kDa. Isoelectric focusing yielded pI of 3–4. Enzyme inhibition by phenylmethylsulfonyl fluoride (PMSF) and aprotinin
confirmed the serine protease nature of the enzyme. K
m, V
max, and K
cat of the enzyme were 4.727 × 10−2 mg/ml, 394.68 U, and 4.2175 × 10−2 s−1, respectively. Enzyme was noted to be active over a broad range of pH (6–12) and temperature (15–65°C), with maximum activity
at pH 11 and 60°C. CaCl2 (1 mM), starch (1%), and sucrose (1%) imparted thermal stability at 65°C. Hg2+, Cu2+, Fe3+, Zn2+, Cd+, and Al3+ inhibited enzyme activity, while 1 mM Co2+ enhanced enzyme activity. Reducing agents enhanced enzyme activity at lower concentrations. The enzyme showed considerable
storage stability, and retained its activity in the presence of hydrocarbons, natural oils, surfactants, and most of the organic
solvents tested. Results indicate that the marine protease holds potential for use in the detergent industry and for varied
applications. 相似文献
14.
A constitutive level of a mycelium-bound lipolytic activity from Aspergillus niger MYA 135 was strongly increased by 97% in medium supplemented with 2% olive oil. The constitutive lipase showed an optimal
activity in the pH range of 3.0–6.5, while the mycelium-bound lipase activity produced in the presence of olive oil had two
pH optima at pH 4 and 7. Interestingly, both lipolytic sources were cold-active showing high catalytic activities in the temperature
range of 4–8°C. These mycelium-bound lipase activities were also very stable in reaction mixtures containing methanol and
ethanol. In fact, the constitutive lipase maintained almost 100% of its activity after exposure by 1 h at 37°C in ethanol.
A simple methodology to evaluate suitable transesterification activities in organic solvents was also reported. 相似文献
15.
Mika Murata Masaru Nagai Makoto Takao Akira Suzuki Takuo Sakai Takao Terashita 《Mycoscience》2001,42(5):479-482
Trehalase from the culture filtrate ofLentinula edodes was purified and characterized. Molecular masses were estimated to be 158 kDa and 79–91 kDa by gel filtration and SDS-PAGE
under the reduced condition, respectively. The enzyme was composed of two identical subunits and contained carbohydrate molecules.
The optimum temperature and pH were obtained at around 40°C and pH 5.0, respectively. The enzyme was stable up to 40°C and
in a range pH of 4–10 at 30°C. It cleaved α-1,1 linkages of trehalose, but not α-1,4, α-1,6 or β-1,4 glycosyl linkages, and
was defined as an acid trehalase. 相似文献
16.
The gene encoding a cold-active and xylose-stimulated β-glucosidase of Marinomonas MWYL1 was synthesized and expressed in Escherichia coli. The recombinant enzyme (reBglM1) was purified and characterized. The molecular mass of the purified reBglM1 determined by
SDS-PAGE agree with the calculated values (50.6 Da). Optima of temperature and pH for enzyme activity were 40°C and 7.0, respectively.
The enzyme exhibited about 20% activity at 5°C and was stable over the range of pH 5.5–10.0. The presence of xylose significantly
enhanced enzyme activity even at higher concentrations up to 600 mM, with maximal stimulatory effect (about 1.45-fold) around
300 mM. The enzyme is active with both glucosides and galactosides and showed high catalytic efficiency (k
cat = 500.5 s−1) for oNPGlc. These characterizations enable the enzyme to be a promising candidate for industrial applications. 相似文献
17.
Characterization of proteolytic bacteria from the Aleutian deep-sea and their proteases 总被引:1,自引:0,他引:1
Xiong H Song L Xu Y Tsoi MY Dobretsov S Qian PY 《Journal of industrial microbiology & biotechnology》2007,34(1):63-71
Six deep-sea proteolytic bacteria taken from Aleutian margin sediments were screened; one of them produced a cold-adapted neutral halophilic protease. These bacteria belong to Pseudoalteromonas spp., which were identified by the 16S rDNA sequence. Of the six proteases produced, two were neutral cold-adapted proteases that showed their optimal activity at pH 7–8 and at temperature close to 35°C, and the other four were alkaline proteases that showed their optimal activity at pH 9 and at temperature of 40–45°C. The neutral cold-adapted protease E1 showed its optimal activity at a sodium chloride concentration of 2 M, whereas the activity of the other five proteases decreased at elevated sodium chloride concentrations. Protease E1 was purified to electrophoretic homogeneity and its molecular mass was 34 kDa, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weight of protease E1 was determined to be 32,411 Da by mass spectrometric analysis. Phenylmethyl sulfonylfluoride (PMSF) did not inhibit the activity of this protease, whereas it was partially inhibited by ethylenediaminetetra-acetic acid sodium salt (EDTA-Na). De novo amino acid sequencing proved protease E1 to be a novel protein. 相似文献
18.
A novel nonionic surfactant- and hydrophilic solvent-stable alkaline serine protease was purified from the culture supernatant
of Serratia sp. SYBC H with duckweed as nitrogen source. The molecular mass of the purified protease is about 59 kDa as assayed via SDS-PAGE.
The protease is highly active over the pH range between 5.0 and 11.0, with the maximum activity at pH 8.0. It is also fairly
active over the temperature range between 30 and 80°C, with the maximum activity at 40°C. The protease activity was substantially
stimulated by Mn2+ and Na+ (5 mM), up to 837.9 and 134.5% at 40°C, respectively. In addition, Mn2+ enhanced the thermostability of the protease significantly at 60°C. Over 90% of its initial activity remained even after
incubating for 60 min at 40°C in 50% (v/v) hydrophilic organic solvents such as DMF, DMSO, acetone and MeOH. The protease
retained 81.7, 83.6 and 76.2% of its initial activity in the presence of nonionic surfactants 20% (v/v) Tween 80, 25% (v/v)
glycerol and Triton X-100, respectively. The protease is strongly inhibited by PMSF, suggesting that it is a serine protease.
Washing experiments revealed that the protease has an excellent ability to remove blood stains. 相似文献
19.
Junpei Zhou Pengjun Shi Rui Zhang Huoqing Huang Kun Meng Peilong Yang Bin Yao 《Journal of industrial microbiology & biotechnology》2011,38(4):523-530
A pH-stable and protease-resistant xylanase (XynB119) was identified from Streptomyces sp. TN119, a strain isolated from the gut luminal contents of longhorned beetle (Batocera horsfieldi) larvae. Using the GC TAIL-PCR method, the 1,026-bp coding gene (xynB119) with 67.3% GC content was successfully cloned and expressed in Escherichia coli. It encodes a 341-residue polypeptide with a calculated molecular mass of 35.9 kDa, including a putative 41-residue signal
peptide, a catalytic domain of glycosyl hydrolase (GH) family 11, a short Gly/Pro-rich linker, and a family 2 cellulose-binding
domain (CBM 2). The deduced amino acid sequence is most similar to (61.9% identity) an endo-1,4-β-xylanase from Streptomyces thermoviolaceus OPC-520. Purified recombinant XynB119 exhibited peak activity at 50°C and pH 7.0, remained stable over a broad pH range (retaining >70%
activity after incubation at pH 1.0–11.0 for 1 h at 37°C without substrate), had strong protease resistance (retaining >90%
activity after proteolytic treatment at 37°C for 1 h) and SDS resistance (at 100 mM). These properties make XynB119 promising
for application in the feed industry and valuable for basic research. Compared to r-XynB119, the r-XynB119 derivative without
CBM 2 and linker region (r-XynB119d) exhibited a decreased pH stability of >25% at extreme pHs (pH 1.0–3.0 and pH 11.0–12.0). 相似文献
20.
A gene encoding an intracellular glucoamylase was identified in the genome of the extreme thermoacidophilic Archaeon Thermoplasma acidophilum. The gene taGA, consisting of 1,911 bp, was cloned and successfully expressed in Escherichia coli. The recombinant protein was purified 22-fold to homogeneity using heat treatment, anion-exchange chromatography, and gel
filtration. Detailed analysis shows that the glucoamylase, with a molecular weight of 66 kDa per subunit, is a homodimer in
its active state. Amylolytic activity was measured over a wide range of temperature (40–90°C) and pH (pH 3.5–7) and was maximal
at 75°C and at acidic condition (pH 5). The recombinant archaeal glucoamylase uses a variety of polysaccharides as substrate,
including glycogen and amylose. Maximal activity was measured towards amylopectin with a specific activity of 4.2 U/mg and
increased almost threefold in the presence of manganese. Calcium ions have a pronounced effect on enzyme stability; in the
presence of 5 mM CaCl2, the half-life increased from 15 min to 2 h at 80°C. 相似文献