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1.
The amino acid sequences of xylanase B (XlnB) and xylanase C (XlnC) from Streptomyces lividans show significant homology. However, the temperature optima and stabilities of the two enzymes are quite different. XlnB exhibits
an optimum temperature of 40 °C and retains 50% of its maximum activity at 43 °C, whereas the corresponding values for XlnC
are 60 and 70 °C. To analyze these properties further, as well as to study the effect of the exchange of homologous segments in the C-terminal region, four chimeras designated as BSC, BFC, CSB, and CFB were constructed by substituting
segments from the C-terminal homologous region of XlnB gene with that of XlnC and in turn substituting XlnC gene with that
of XlnB. The purified chimeric enzymes were characterized with respect to pH/temperature activity, stability, and kinetic
parameters. Most of enzymatic properties of chimeras were admixtures of those of the two parents. The chimeric enzymes were
optimally active at 45–55 °C and pH 7.0. Both K
m and k
cat values of chimeric enzymes for p-nitrophenyl-β-d-cellobioside were admixtures of both parental enzymes, except that the k
cat value of chimeric BFC (2.79 s−1) was higher than that of parental XlnC (1.99 s−1). Notably, thermal stability of chimeric BSC and BFC was increased by 25 and 13 °C separately, as compared to one of parental XlnB, whereas
the thermal stability of chimeric CSB and CFB was decreased by 23 and 21 °C, respectively, as compared to another parental
XlnC. These results suggest that homologous C-terminal region in S. lividans GH11 xylanase appears to play an important role in determining enzyme characteristics, and exchanging of different segments of gene in this region might significantly alter or improve the enzymatic properties such as thermal
stability. 相似文献
2.
Kazutoshi Shindo Ryoko NakamuraIkuko Chinda Yasuo OhnishiSueharu Horinouchi Haruko TakahashiKazuo Iguchi Shigeaki HarayamaKensuke Furukawa Norihiko Misawa 《Tetrahedron》2003,59(11):1895-1900
The bphA1(2072)A2A3A4 gene cluster codes for a shuffled biphenyl dioxygenase holoenzyme with broad substrate specificity. These bphA1(2072)A2A3A4 genes were expressed in the actinomycetes Streptomyces lividans using a thiostrepton-inducible promoter PtipA. Biotransformation experiments of various aromatics including carboxylic acid or amine in their molecular structure, such as 1-naphthoic acid, 2-(1-naphthyl)acetic acid, diphenylamine, and 1-benzyl-4-piperidone, were performed using the recombinant S. lividans cells. These ionized aromatics were converted to the corresponding 1,2-dihydrodiol, mono- or tri-hydroxy forms in 48 h. The structure of the converted products was determined by their EI-MS, 1H- and 13C NMR analysis, and several products were found to be novel compounds. 相似文献
3.
Leda M. F. Gottschalk Jacyara M. B. Macedo Elba P. S. Bon 《Applied biochemistry and biotechnology》1999,79(1-3):771-778
Lignin peroxidase (LiP) production cost should be reduced to justify its use in the control of environmental pollution. In
this work, we studied the enzyme production by Streptomyces viridosporus T7A using glucose or corn oil as a carbon source having 0.65% yeast extract as a nitrogen source. Enzyme activity, observed
using either 0.65% glucose or corn oil at 0.1, 0.5, and 1.0% concentration, was 300, 150, 300, and 200 U/L, respectively.
Although higher enzyme activity was obtained in both media containing 0.65% glucose and 0.5% corn oil, the use of corn oil
resulted in a better LiP stability. When combined carbon sources were used, higher values of enzyme activity (360, 350, and
225 U/L) were observed in media with 0.65% glucose and supplemented with 0.1, 0.5, and 1.0% corn oil, respectively. Although
the presence of both glucose and 0.5% corn oil is favorable for LiP production, satisfactory results in terms of enzyme production
and stability could be also observed using 0.5% corn oil as a sole carbon source, which may lead to reduced production costs
of the LiP enzyme. 相似文献
4.
G. P. Girina N. M. Alpatova L. G. Feoktistov 《Russian Journal of Electrochemistry》2006,42(1):102-105
In the cyclic voltamograms for electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene at its concentrations of 5 and 10 mM in dimethylformamide solution of 0.1 M Bu4NBF4, taken at glassy-carbon electrode, four current peaks corresponding to consecutive stages of the reduction process are observed for the first time. The many times repeated potential cycling from 0 V (SCE) to the value approaching the 2nd peak potential results in the electrode passivation; a film of the intermediate product of the α,α,α′,α′-tetrabromo-p-xylene reduction is deposited at the electrode, whose composition may be-(BrCH-C6H4-CHBr-BrCH-C6H4-CHBr)n-. When the electrode covered with the deposited film is transferred to a solution of the same composition, in which the primary cycling was performed, yet free from α,α,α′,α′-tetrabromo-p-xylene, and underwent to potential cycling up to ?2V, the first cycle demonstrates a current peak that is due to the film reduction. A redox-active poly(p-phenylenevinylene) forms at the electrode. 相似文献
5.
The electrochemical behavior of a film, which consists of intermediate products of the α,α,α′,α′-tetrabromo-para-xylol (TBX) reduction and is deposited on a glassy-carbon electrode from 5 × 10?2 M TBX solutions, is studied in 0.1 M Bu4NBF4 solution in DMFA by cycling the potential from 0 to ?1.4 V with respect to an aqueous saturated calomel electrode. When the potential is cycled from 0 to ?2.1 V in a cell filled with the supporting electrolyte, the film, which is assumed to have the (-BrHC-C6H4-CHBr-)n composition, can be reduced to form poly(para-phenylenevilylene) (PPV). This film exhibits redox activity in the cathodic range in solutions of Bu4NBF4 in DMFA and in both cathodic and anodic ranges in solutions of Bu4NBF4 in AN. It is observed for the first time that, if the cathodic limit of the potential cycling range is extended to ?2.5 V, the cathodic doping of PPV at potentials below ?2 V disappears and a new reversible redox process takes place at more negative potentials. 相似文献
6.
The title cations were produced in aqueous solution by chemical initiation (solvolysis) of benzyl-gem-dihalides and benzyl-gem-diazides. The solvolysis reactions of benzyl-gem-dihalides and benzyl-gem-diazides in water proceed by a stepwise mechanism through α-halobenzyl carbocation and α-azidobenzyl carbocation intermediates,
which are captured by water to give the corresponding carbonyl compounds as the sole detectable products. Rate constant ratiok
x/ks(M−1) for partitioning of the carbocation between reaction with halide/azide ion and reaction with water is determined by analysis
of halide/azide common ion inhibition of the solvolysis reaction. The rate constantsk
s(s-1) for the reaction of the cation with solvent water were determined from the experimental values ofk
x/ks andk
solv, for the solvolysis of the benzyl-gem-dihalides and benzyl-gem-diazides respectively, usingk
x = 5 × 109M−1 s−1 for diffusion-limited reaction of halide/azide ion with α-substituted benzyl carbocations. The values of 1/k
s are thus the lifetimes of the α-halobenzyl carbocations and α-azidobenzyl carbocations respectively. 相似文献
7.
T. V. Kharlamova 《Chemistry of Natural Compounds》2007,43(4):391-394
The alkylation of 1,6,8-trihydroxy-3-methylanthraquinone (frangula-emodin) by α-bromoalkylmethylketones was investigated. Hydroxyls in the 1-and 8-positions of the β-derivatives were O-acylated. The compositions and structures of the prepared compounds were confirmed by elemental analysis and UV, IR, PMR,
and 13C NMR spectroscopy.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 324–326, July–August, 2007. 相似文献
8.
Báez-Vásquez MA Adrio JL Piret JM Demain AL 《Applied biochemistry and biotechnology》1999,81(3):145-152
Resting cells of Streptomyces clavuligerus NP-1, which posses deacetoxy-cephalosporin C synthase activity, have been shown previously to perform oxidative ring expansion
of penicillin G in the presence of iron, ascorbic acid, and α-ketoglutaric acid to form deacetoxycephalosporin G. Further
studies on this bioconversion indicated that use of MOPS or HEPES buffer at pH 6.5 more than doubled the extent of the reaction
observed with the previously used Tris-HCl at pH 7.4. Levels of bioconversion as high as 16.5% were achieved at low penicillin
G concentrations. Previously, conversion yields were <1%. 相似文献
9.
Juan Manuel Benito David Rodríguez-Lucena José Luis Jiménez Blanco Carmen Ortiz Mellet José Manuel García Fernández 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):147-150
A new concept for the de novo synthesis of artificial glyconanocavities is presented. The use of alternating α,α′-trehalose building blocks and (thio)urea segments allows the efficient synthesis of a new family of cyclooligosaccharides,
namely cyclotrehalans (CTs), featuring a convex-shaped cavity with an apolar environment. CTs are designed to exhibit molecular inclusion abilities
similar to that of cyclodextrins (CDs). Contrary to CDs, CTs expose the monosaccharide β-face to the inner cavity, while the (thio)urea tethers provides some conformational adaptability. High-yielding syntheses
of a series of CTs and a preliminary evaluation of their inclusion properties are reported. 相似文献
10.
G. Ozek T. Ozek K. H. C. Baser E. Hamzaoglu A. Duran 《Chemistry of Natural Compounds》2007,43(6):667-671
The component composition of essential oils produced by steam distillation from flower heads, leaves, and stems of Salvia anatolica (Lamiaceae), a recently described new species endemic from Turkey, was studied by GC/FID and GC/MS. A total of 127 volatile
components representing 96% of the oil was identified in essential oil from flower heads and leaves. It was found that the
principal oil components of flower heads and leaves were α-pinene (10.9%), β-pinene (6.7%), α-copaene (6.3%), heptacosane (6.2%), and hexadecanoic acid (5.0%). A total of 109 volatile compounds representing 87.9% of
the oil was characterized in essential oil isolated from stems. The principal oil components of stems were identified as hexadecanoic
acid (27.2%), tetradecanoic acid (15.2%), dodecanoic acid (5.5%), and α-copaene (5.0%).
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 552–555, November–December, 2007. 相似文献
11.
Cyclopentanone or cyclohexanone were condensed with aromatic aldehydes to give corresponding α,α′-bis(R-benzylidene)cyclopentanones or α,α′-bis(R-benzylidene)cyclohexanones. The reaction was catalyzed by potassium hydrogen sulfate with a yield of 84–95% under
solvent-free conditions. 相似文献
12.
I. M. Chung Mohd Ali A. Ahmad C. Y. Yu K. H. Ma J. G. Gwag Y. J. Park 《Chemistry of Natural Compounds》2005,41(6):650-653
One new compound 3,7,11,15,19-pentamethyl-9α,10α,11α,17α,18α-pentahydroxy-n-tetracosan-1-oxy-p-hydroxycaffeoate (oryzaterpenyl
caffeoate) (1), together with three known fatty acids linoleic acid, stearic acid and myristic acid were isolated and identified from the
rice grain of Oryza sativa. The structure of the new compound was elucidated by 1D and 2D NMR spectroscopic techniques (1H-1HCOSY, 1H-13C HETCOR) aided by EI-MS, and IR spectra.
__________
Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 535–537, November–December, 2005. 相似文献
13.
M. I. Merlani L. Sh. Amiranashvili N. I. Men’shova E. P. Kemertelidze 《Chemistry of Natural Compounds》2007,43(1):97-99
5α-Androstan-3β,17β-diol (3b-adiol), a known inhibitor of prostate cancer cell growth, was synthesized from tigogenin. Its structure was confirmed
by NMR and IR spectroscopy and mass spectroscopy.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 81–82, January–February, 2007. 相似文献
14.
The optimization of nutrient levels for the production of pristinamycins by Streptomyces pristinaespiralis CGMCC 0957 in submerged fermentation was carried out using the statistical methodologies based on the Plackett–Burman design,
the steepest ascent method, and the central composite design (CCD). First, the Plackett–Burman design was applied to evaluate
the influence of related nutrients in the medium. Soluble starch and MgSO4·7H2O were then identified as the most significant nutrients with a confidence level of 99%. Subsequently, the concentrations
of the two nutrients were further optimized using response surface methodology of CCD, together with the steepest ascent method.
Accordingly, a second-order polynomial regression model was finally fitted to the experimental data. By solving the regression
equation from the model and analyzing the response surface, the optimal levels for soluble starch and MgSO4·7H2O were determined as 20.95 and 5.67g/L, respectively. Under the optimized medium, the yield of pristinamycins in the shake
flask and 5-L bioreactor could reach 1.30 and 1.01g/L, respectively, which is the highest yield reported in literature to
date. 相似文献
15.
N. N. Sidamonidze L. K. Janiashvili R. O. Vardiashvili R. A. Gakhokidze 《Chemistry of Natural Compounds》2006,42(2):127-128
A new synthesis of certain lactam-containing N-glycosides was developed. 2,3,4,6-Tetra-O-acetyl-β-D-gluco(galacto)pyranosylcaprolactams and 2,3,4,6-tetra-O-acetyl-β-D-gluco(galacto)pyranosylpyrrolidones were synthesized by condensation at room temperature of acetobromoglucose and acetobromogalactose
with ɛ-caprolactams and α-pyrrolidone.
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Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 105–106, March–April, 2006. 相似文献
16.
Bergquist Peter L. Te’o V. S. Junior Gibbs Moreland D. Cziferszky Angela C. E. De Faria Fabricia P. Azevedo Maristela O. Nevalainen K. M. Helena 《Applied biochemistry and biotechnology》2002,98(1-9):165-176
Cost-effective production of enzymes for industrial processes makes the appropriate selection of the host-vector expression
system critical. We have developed two systems for the bulk production of bleaching enzymes from thermophiles. Kluyveromyces lactis has been developed as a secretion host employing expression vectors based on the 2μ-like plasmid pKD1 of Kluyveromyces drosophilarium. Our second system involves the filamentous fungus Trichoderma reesei. Fusion and nonfusion vectors have been constructed using the strong cellobiohydrolase 1 (cbh1) promoter. The KEX2 protease cleavage site and a 6 × HIS-tag have been incorporated to facilitate both cleavage and purification
of the mature foreign proteins. 相似文献
17.
Flávio José L. dos Santos Antônio Flávio de C. Alcântara Dalton L. Ferreira-Alves Dorila Piló-Veloso 《Structural chemistry》2008,19(4):625-631
This work describes the synthesis of new derivatives of 6α,7β-dihydroxyvouacapan-17β-oic acid (1) employing the Swern method for the oxidation of C-6 and C-7 of methyl 6α,7β-di-hydroxyvouacapan-17β-oate (2) and the formation of methyl 6,7-dioxovouacapan-17β-oate (3). NMR structural studies associated with theoretical calculations of reaction intermediates and products are also reported.
The mixture of methyl 7β-hydroxy-6-oxovouacapan-17β-oate (4; 21%) and methyl 6α-hydroxy-7-oxovouacapan-17β-oate (5; 79%) was the product from the first step of the oxidation of 2. The lower energy of 5, calculated by HF/6-31G* and DFT/BLYP/6-31G* methods, reinforces the thermodynamic control proposed for the reaction. After
further Swern oxidation of the mixture of 4 and 5, the isomeric form methyl 6-hydroxy-7-oxovouacap-5-en-17β-oate (6) was obtained. Theoretical calculations indicate a lower energy for the mono-enol 6 than the 1,2-diketo 3 and the other mono-enol methyl 7-hydroxy-6-oxovouacap-7-en-17β-oate (7). 相似文献
18.
The needle oils of Pinus sylvestris L. were analyzed by GC and GC-MS. The results showed some qualitative and quantitative variations. Forty-three components
were identified in the oils of P. sylvestris. All the samples of essential oils contained α-pinene, camphene, and β-pinene as major constituents. Chemical variations
of P. sylvestris samples were discussed.
Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 22–25, January–February, 2006. 相似文献
19.
Celso Ricardo Denser Pamboukian Maria Câandida Reginato Facciotti 《Applied biochemistry and biotechnology》2004,112(2):111-121
Fed-batch runs were performed in order to correlate the production of retamycin, an anthracycline antibiotic produced by Streptomyces olindensis in submerged cultures, with the specific growth rate. Maximum retamycin production was achieved with an exponential feed
rate, controlling the specific growth rate at a low value (0.03h−1, about 10% of the maximum specific growth rate). Control of the specific growth rate at higher values (0.10 and 0.17 h−1) caused a decrease in antibiotic production. Morphology, assessed by image analysis, was shown to be highly relevant in this
process. Cell growth mainly in the form of clumps (90% clumps and 10% free filaments) led to better results than growth as
clumps (75%) and free filaments (25%). 相似文献
20.
Kjell Nilsson Peter Brodelius Klaus Mosbach 《Applied biochemistry and biotechnology》1982,7(1-2):47-49
The yeast,Trigonopsis variabilis, was immobilized by entrapment in alginate. The immobilized cells containing high amounts of D-amino acid oxidase were used
to convert D-amino acids to their corresponding α-keto acids. 相似文献