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1.
Ziziphora tenuior L. (Lamiaceae) is an aromatic herb used for its medicinal values against fungi, bacteria. Micropropagation can be used for large-scale multiplication of essential oil producing plants thus avoiding an overexploitation of natural resources. This work aims to develop a reliable protocol for the in vitro propagation of Z. tenuior, and to compare the antioxidant activity between in vitro propagated and wild plants.The explants were sterilized and cultured on MS medium containing different concentrations of growth regulators naphthalene acetic acid (NAA) or indole-3-butyric acid (IBA) with 0.5 mg/L of kinetin (Kin) callus formation was 70.2% after 45 days of incubation in dark on medium supplemented with 1.5 mg/L of NAA. After one month of callus culture on medium supplemented with 2 mg/L BA the shoot number was 5.12 and for the multiplication stage. The shoot number was 4.21 and length was 6.17 cm on medium supplemented with 1 mg/L Kin + 0.1 mg/L NAA.DPPH• reagent was used to test the antioxidant activity. The aqueous and methanol extracts of in vitro plants which were treated with 1.5 and 1 mg/L of kin plus 0.1 mg/L of NAA showed a strong DPPH• scavenging activity where IC50 was 0.307 and 0.369 mg/ml, respectively, while the IC50 of aqueous and methanol extracts of wild plants was 0.516 and 9.229 mg/ml, respectively. Our results suggested that plant growth regulators and in vitro culture conditions increased the antioxidant activity.  相似文献   

2.
The mevalonate-based isoprenoid biosynthetic pathway is responsible for producing cholesterol in humans and is used commercially to produce drugs, chemicals, and fuels. Heterologous expression of this pathway in Escherichia coli has enabled high-level production of the antimalarial drug artemisinin and the proposed biofuel bisabolane. Understanding the kinetics of the enzymes in the biosynthetic pathway is critical to optimize the pathway for high flux. We have characterized the kinetic parameters of phosphomevalonate kinase (PMK, EC 2.7.4.2) from Saccharomyces cerevisiae, a previously unstudied enzyme. An E. coli codon-optimized version of the S. cerevisiae gene was cloned into pET-52b+, then the C-terminal 6X His-tagged protein was expressed in E. coli BL21(DE3) and purified on a Ni2+ column. The KM of the ATP binding site was determined to be 98.3 µM at 30°C, the optimal growth temperature for S. cerevisiae, and 74.3 µM at 37°C, the optimal growth temperature for E. coli. The KM of the mevalonate-5-phosphate binding site was determined to be 885 µM at 30°C and 880 µM at 37°C. The Vmax was determined to be 4.51 µmol/min/mg enzyme at 30°C and 5.33 µmol/min/mg enzyme at 37°C. PMK is Mg2+ dependent, with maximal activity achieved at concentrations of 10 mM or greater. Maximum activity was observed at pH = 7.2. PMK was not found to be substrate inhibited, nor feedback inhibited by FPP at concentrations up to 10 µM FPP.  相似文献   

3.
The Santalum peroxidase was extracted from the leaves and precipitated with double volume of chilled acetone. The optimum percent relative activity for the Santalum peroxidase was observed at pH 5.0 and 50 °C temperature. The Santalum peroxidase per cent relative activity was stimulated in the presence of phenolic compounds like ferrulic acid and caffeic acids; however, indole-3-acetic acid (IAA) and protocatechuic acid act as inhibitors. All divalent cations Fe2+, Mn2+, Mg2+, Cu2+ and Zn2+ stimulate the relative activity of the Santalum peroxidase at concentration of 2.0 μM. Amino acids like L-alanine and L-valine activate the per cent relative activity, while L-proline and DL-methionine showed moderate inhibition for the Santalum peroxidase. However, a very low a concentration of cysteine acts as a strong inhibitor of Santalum peroxidase at the concentration of 0.4 mM. Native polyacrylamide gel electrophoresis (Native-PAGE) was performed for isoenzyme determination and two bands were observed. Km and Vmax values were calculated from Lineweaver-Burk graph. The apparent Vmax/Km value for O-dianisidine and H2O2 were 400 and 5.0 × 105 Units/min/mL respectively.  相似文献   

4.
5.
Zingiber cassumunar is an important plant used in traditional medicine and as a natural mosquito repellent. However, the compounds responsible for the repellent activity of the plant are still unknown. The aim of the study is to identify the components of Z. cassumunar essential oil that show repellent activity against Aedes albopictus. We also evaluated the larvicidal and adulticidal activities of Z. cassumunar essential oil against Ae. albopictus. In-cage mosquito repellent experiments showed that Z. cassumunar essential oil possessed moderate repellent activity with a minimum effective dose (MED) of 0.16 ± 0.01 mg/cm2, compared to reference standard N,N-diethyl-3-methylbenzamide (DEET, 0.03 ± 0.01 mg/cm2). Bioassay-guided fractionation identified the major active compound of Z. cassumunar essential oil as (−)-terpinen-4-ol (1) (MED: 0.19 ± 0 mg/cm2). We also found that Z. cassumunar essential oil showed moderate larvicidal activity against first instar larvae of Ae. albopictus with a LC50 (50% lethal concentration) of 44.9 μg/L after 24 h. Fumigation bioassays showed that Z. cassumunar essential oil exhibits moderate adulticidal activity against Ae. albopictus with a LC50 of 5.44%, while (−)-terpinen-4-ol showed significant adulticidal activity with a LC50 of 2.10% after 24 h. This study verifies that the Z. cassumunar essential oil has mosquito repellent activity, and that (−)-terpinen-4-ol is mainly responsible for this activity. Furthermore, this study provides scientific support for the folk usage of Z. cassumunar essential oil as mosquito repellent and indicates that Z. cassumunar essential oil and (−)-terpinen-4-ol can be used as plant-derived repellents and insecticides for mosquito control.  相似文献   

6.
Salacia oblonga, an inhabitant of tropical regions has been used in traditional Indian medicinal systems. Phytochemicals were extracted in methanol from the plant and analyzed for various biological activities. The results of biochemical tests for total phenolics (297 ± 0.005 and 275 ± 0.006) and flavonoids (95 ± 0.004 and 61.6 ± 0.004) in the aerial and root parts were indicated as Gallic acid and quercetin equivalents respectively. The Aerial and root extracts showed strong reducing ability based on reducing power and FRAP assays. The extracts exhibited significant IC50 values in DPPH, super oxide and nitric oxide radical scavenging assays. The extracts displayed low IC50 values (<50 μg/ml) when assessed for antiproliferative activity against breast cancer cell lines using the MTT assay. GC-MS analysis of methanolic extracts have revealed the presence of compounds viz. n-Hexadecanoic acid, N-Methoxy-N-methylacetamide, Ursa-9(11), 12-dien-3-ol, Gamma-sitosterol etc., that might be potential candidates for the biological activity exhibited by the extract.

Electronic supplementary material

The online version of this article (doi:10.1007/s12298-015-0317-z) contains supplementary material, which is available to authorized users.Keyword: Salacia oblonga, Antioxidant activity, Free radical scavenging activity, Reactive oxygen species, Antiproliferative activity  相似文献   

7.
Bacterial laccases are ideal alternatives of fungal laccases for specific industrial applications due to specific characteristics such as alkalescence dependence and high chloride tolerance. However, some bacterial laccases presented as inclusion bodies when expressing in Escherichia coli and showed thermal instability. In this study, rational design was employed to enhance the solubility and the thermostablity of the bacterial laccase Lac15-His6 based on the crystal structure obtained previously. After deletion of His-tag and residues323–332, the obtained Lac15D was completely expressed in soluble form even at a higher temperature of 28°C, compared to only 50% of Lac15-His6 expressed solubly at 16°C. It showed a two-time higher activity at temperatures lower than 35°C and a half-life increasing from 72 min to 150 min at 45°C. When used in chromogenic reactions, Lac15D showed constant activity toward dye precursors and their combinations under alkaline conditions, demonstrating its application potential in hair coloring biotechnology.  相似文献   

8.
Purvis AC 《Plant physiology》1988,86(2):623-625
The capacity of the alternative respiratory pathway increased in the flavedo tissue of `Marsh' grapefruit (Citrus paradisi Macf.) stored at 5°C for 2 weeks or longer. Elevated O2 levels during respiratory assays enhanced respiration by the tissue at 20°C but not at 5°C. At 20°C, salicylhydroxamic acid alone was inhibitory to O2 uptake only in elevated O2. In conventional Warburg studies, alternative pathway respiration may be limited by the low solubility and/or slow rate of O2 diffusion into plant tissues, such as grapefruit flavedo, and may be responsible for the apparent low utilization of the alternative pathway potential observed in other studies.  相似文献   

9.
1. The speed of transmission of the activation wave along passive iron wires enclosed in glass tubes containing dilute (70 per cent) nitric acid increases with the conductivity (sectional area) of the column of electrolyte but at a slower rate. The speed is closely proportional to the square root of the conductivity See PDF for Equation. The reasons for this relationship are discussed and an explanation is proposed. 2. The recovery of transmissivity after the passage of an activation wave is gradual and follows a characteristic course. After an interval of partial or decremental transmission (having a high temperature coefficient and lasting several minutes at 20°), the wire recovers its power of transmitting an activation wave for an indefinite distance. In such a recovered wire the speed of transmission is at first slow and increases by degrees up to a maximum, the increase following a curve apparently of the type vt = v 0 (1 – e_kt). The approximate time required to attain this maximum (corresponding to complete recovery) at the different temperatures is 15 to 20 minutes at 20°, 30 to 45 minutes at 15°, ca. 60 minutes at 10°, and 90 minutes or more at 5°. 3. The character of the curve of recovery (the curve relating speed of transmission to interval since previous activation) agrees with the assumption that the increase in speed depends on a progressive chemical change in the molecules forming the passivating film, this change involving the transformation of (relatively) nonreactive into reactive molecules and following the course of a monomolecular reaction. 4. The temperature coefficient of the speed of transmission (between 5° and 20°) is low, of the order Q 10 = 1.3 to 1.6. That of the rate of recovery, on the contrary, is high (Q 10 = ca. 3). The parallel to the conditions in nerve and other transmitting protoplasmic systems is pointed out and discussed. 5. Passive wires enclosed in acid-containing continuous and interrupted glass tubes immersed in a large volume of acid exhibit characteristic phenomena of distance action; under appropriate conditions the velocity of transmission of the activating influence between different areas may thus be greatly increased. Characteristic instances are cited and some possible physiological parallels are pointed out.  相似文献   

10.
11.
Nitrogen (N) serves as an important mineral element affecting plant productivity and nutritional quality. However, few studies have addressed the interactive effects of elevated CO2 and precipitation change on leaf N of dominant grassland genera such as Stipa L. This has restricted our understanding of the responses of grassland to climate change. We simulated the interactive effects of elevated CO2 concentration and varied precipitation on leaf N concentration (Nmass) of four Stipa species (Stipa baicalensis, Stipa bungeana, Stipa grandis, and Stipa breviflora; the most dominant species in arid and semiarid grassland) using open-top chambers (OTCs). The relationship between the Nmass of these four Stipa species and precipitation well fits a logarithmic function. The sensitivity of these four species to precipitation change was ranked as follows: S. bungeana S. breviflora > S. baicalensis S. grandis. The Nmass of S. bungeana was the most sensitive to precipitation change, while S. grandis was the least sensitive among these Stipa species. Elevated CO2 exacerbated the effect of precipitation on Nmass. Nmass decreased under elevated CO2 due to growth dilution and a direct negative effect on N assimilation. Elevated CO2 reduced Nmass only in a certain precipitation range for S. baicalensis (163–343 mm), S. bungeana (164–355 mm), S. grandis (148–286 mm), and S. breviflora (130–316 mm); severe drought or excessive rainfall would be expected to result in a reduced impact of elevated CO2. Elevated CO2 affected the Nmass of S. grandis only in a narrow precipitation range. The effect of elevated CO2 reached a maximum when the amount of precipitation was 253, 260, 217, and 222 mm for S. baicalensis, S. bungeana, S. grandis, and S. breviflora, respectively. The Nmass of S. grandis was the least sensitive to elevated CO2. The Nmass of S. breviflora was more sensitive to elevated CO2 under a drought condition compared with the other Stipa species.  相似文献   

12.
The hemerythrin-like protein from Mycobacterium kansasii (Mka HLP) is a member of a distinct class of oxo-bridged diiron proteins that are found only in mycobacterial species that cause respiratory disorders in humans. Because it had been shown to exhibit weak catalase activity and a change in absorbance on exposure to nitric oxide (NO), the reactivity of Mka HLP toward NO was examined under a variety of conditions. Under anaerobic conditions, we found that NO was converted to nitrite (NO2) via an intermediate, which absorbed light at 520 nm. Under aerobic conditions NO was converted to nitrate (NO3). In each of these two cases, the maximum amount of nitrite or nitrate formed was at best stoichiometric with the concentration of Mka HLP. When incubated with NO and H2O2, we observed NO peroxidase activity yielding nitrite and water as reaction products. Steady-state kinetic analysis of NO consumption during this reaction yielded a Km for NO of 0.44 μM and a kcat/Km of 2.3 × 105 M−1s−1. This high affinity for NO is consistent with a physiological role for Mka HLP in deterring nitrosative stress. This is the first example of a peroxidase that uses an oxo-bridged diiron center and a rare example of a peroxidase utilizing NO as an electron donor and cosubstrate. This activity provides a mechanism by which the infectious Mycobacterium may combat against the cocktail of NO and superoxide (O2•−) generated by macrophages to defend against bacteria, as well as to produce NO2 to adapt to hypoxic conditions.  相似文献   

13.
Wada H  Murata N 《Plant physiology》1990,92(4):1062-1069
Changes in glycerolipid and fatty acid composition with a change in growth temperature were studied in the cyanobacterium, Synechocystis PCC6803. Under isothermal growth conditions, temperature did not significantly affect the composition of the various classes of lipids, but a decrease in temperature altered the degree of unsaturation of C18 acids at the sn-1 position, but not that of C16 acids at the sn-2 position of the glycerol moiety in each class of lipids. When the growth temperature was shifted from 38°C to 22°C, the desaturation of C18 acids, but not that of C16 acids, was stimulated. The desaturation of fatty acids occurred only in the light and was inhibited by chloramphenicol, rifampicin and 3-(3,4-dichlorophenyl)-1, 1-dimethylurea, but not by cerulenin, an inhibitor for fatty acid synthesis. These findings suggest that desaturase activities are induced after a shift from a higher to a lower temperature, and that the desaturation of fatty acids is connected with the reactions involved in photosynthetic electron transport.  相似文献   

14.
Enzymes that are used as animal feed supplements should be able to withstand temperatures of 60 to 90°C, which may be reached during the feed pelleting process. The thermostability properties of three histidine acid phosphatases, Aspergillus fumigatus phytase, Aspergillus niger phytase, and A. niger optimum pH 2.5 acid phosphatase, were investigated by measuring circular dichroism, fluorescence, and enzymatic activity. The phytases of A. fumigatus and A. niger were both denatured at temperatures between 50 and 70°C. After heat denaturation at temperatures up to 90°C, A. fumigatus phytase refolded completely into a nativelike, fully active conformation, while in the case of A. niger phytase exposure to 55 to 90°C was associated with an irreversible conformational change and with losses in enzymatic activity of 70 to 80%. In contrast to these two phytases, A. niger pH 2.5 acid phosphatase displayed considerably higher thermostability; denaturation, conformational changes, and irreversible inactivation were observed only at temperatures of ≥80°C. In feed pelleting experiments performed at 75°C, the recoveries of the enzymatic activities of the three acid phosphatases were similar (63 to 73%). At 85°C, however, the recovery of enzymatic activity was considerably higher for A. fumigatus phytase (51%) than for A. niger phytase (31%) or pH 2.5 acid phosphatase (14%). These findings confirm that A. niger pH 2.5 acid phosphatase is irreversibly inactivated at temperatures above 80°C and that the capacity of A. fumigatus phytase to refold properly after heat denaturation may favorably affect its pelleting stability.  相似文献   

15.
The reaction mechanism for the formation of 2′-deoxyoxanosine from 2′-deoxyguanosine by nitrous acid was explored using methyl derivatives of guanosine and an isolated intermediate of the reaction. When 1-methylguanosine was incubated with NaNO2 under acidic conditions, N5-methyloxanosine and 1-methylxanthosine were generated, whereas the same treatment of N2,N2-dimethylguanosine generated no product. In a similar experiment without NO2, participation of a Dimroth rearrangement was ruled out. In the guanosine–HNO2 reaction system, an intermediate with a half-life of 5.6 min (pH 7.0, 20°C) was isolated and tentatively identified as a diazoate derivative of guanosine. The diazoate intermediate was converted into oxanosine and xanthosine at a molar ratio (oxanosine:xanthosine) of 0.26 at pH 7.0 and 20°C. The ratio was not affected by the incubation pH between 2 and 10, but increased linearly with temperature from 0.22 (0°C) to 0.32 (50°C). The addition of acetone also increased the ratio up to 0.85 (98% acetone). Based on these results, a con-ceivable pathway for the formation of 2′-deoxyoxanosine from 2′-deoxyguanosine by HNO2 is proposed.  相似文献   

16.
Spraying mustard (Sinapis alba L.) seedlings with salicylic acid (SA) solutions between 10 and 500 μm significantly improved their tolerance to a subsequent heat shock at 55°C for 1.5 h. The effects of SA were concentration dependent, with higher concentrations failing to induce thermotolerance. The time course of thermotolerance induced by 100 μm SA was similar to that obtained with seedlings acclimated at 45°C for 1 h. We examined the hypothesis that induced thermotolerance involved H2O2. Heat shock at 55°C caused a significant increase in endogenous H2O2 and reduced catalase activity. A peak in H2O2 content was observed within 5 min of either SA treatment or transfer to the 45°C acclimation temperature. Between 2 and 3 h after SA treatment or heat acclimation, both H2O2 and catalase activity significantly decreased below control levels. The lowered H2O2 content and catalase activity occurred in the period of maximum thermoprotection. It is suggested that thermoprotection obtained either by spraying SA or by heat acclimation may be achieved by a common signal transduction pathway involving an early increase in H2O2.  相似文献   

17.
Temperature effects on nocturnal carbon gain and nocturnal acid accumulation were studied in three species of plants exhibiting Crassulacean acid metabolism: Mamillaria woodsii, Opuntia vulgaris, and Kalanchoë daigremontiana. Under conditions of high soil moisture, nocturnal CO2 gain and acid accumulation had temperature optima at 15 to 20°C. Between 5 and 15°C, uptake of atmospheric CO2 largely accounted for acid accumulation. At higher tissue temperatures, acid accumulation exceeded net carbon gain indicating that acid synthesis was partly due to recycling of respiratory CO2. When plants were kept in CO2-free air, acid accumulation based on respiratory CO2 was highest at 25 to 35°C. Net acid synthesis occurred up to 45°C, although the nocturnal carbon balance became largely negative above 25 to 35°C. Under conditions of water stress, net CO2 exchange and nocturnal acid accumulation were reduced. Acid accumulation was proportionally more decreased at low than at high temperatures. Acid accumulation was either similar over the whole temperature range (5-45°C) or showed an optimum at high temperatures, although net carbon balance became very negative with increasing tissue temperatures. Conservation of carbon by recycling respiratory CO2 was temperature dependent. At 30°C, about 80% of the dark respiratory CO2 was conserved by dark CO2 fixation, in both well irrigated and water stressed plants.  相似文献   

18.
Cre recombinase selectively recognizes DNA and prevents non-specific DNA cleavage through an orchestrated series of assembly intermediates. Cre recombines two loxP DNA sequences featuring a pair of palindromic recombinase binding elements and an asymmetric spacer region, by assembly of a tetrameric synaptic complex, cleavage of an opposing pair of strands, and formation of a Holliday junction intermediate. We used Cre and loxP variants to isolate the monomeric Cre-loxP (54 kDa), dimeric Cre2-loxP (110 kDa), and tetrameric Cre4-loxP2 assembly intermediates, and determined their structures using cryo-EM to resolutions of 3.9, 4.5 and 3.2 Å, respectively. Progressive and asymmetric bending of the spacer region along the assembly pathway enables formation of increasingly intimate interfaces between Cre protomers and illuminates the structural bases of biased loxP strand cleavage order and half-the-sites activity. Application of 3D variability analysis to the tetramer data reveals constrained conformational sampling along the pathway between protomer activation and Holliday junction isomerization. These findings underscore the importance of protein and DNA flexibility in Cre-mediated site selection, controlled activation of alternating protomers, the basis for biased strand cleavage order, and recombination efficiency. Such considerations may advance development of site-specific recombinases for use in gene editing applications.  相似文献   

19.
Pseudomonas aeruginosa is a Gram-negative opportunistic human pathogen that is highly prevalent in individuals with cystic fibrosis (CF). A major problem in treating CF patients infected with P. aeruginosa is the development of antibiotic resistance. Therefore, the identification of novel P. aeruginosa antibiotic drug targets is of the utmost urgency. The genome of P. aeruginosa contains four putative cytochrome P450 enzymes (CYPs) of unknown function that have never before been characterized. Analogous to some of the CYPs from Mycobacterium tuberculosis, these P. aeruginosa CYPs may be important for growth and colonization of CF patients’ lungs. In this study, we cloned, expressed, and characterized CYP168A1 from P. aeruginosa and identified it as a subterminal fatty acid hydroxylase. Spectral binding data and computational modeling of substrates and inhibitors suggest that CYP168A1 has a large, expansive active site and preferentially binds long chain fatty acids and large hydrophobic inhibitors. Furthermore, metabolic experiments confirm that the enzyme is capable of hydroxylating arachidonic acid, an important inflammatory signaling molecule present in abundance in the CF lung, to 19-hydroxyeicosatetraenoic acid (19-HETE; Km = 41 μM, Vmax = 220 pmol/min/nmol P450), a potent vasodilator, which may play a role in the pathogen’s ability to colonize the lung. Additionally, we found that the in vitro metabolism of arachidonic acid is subject to substrate inhibition and is also inhibited by the presence of the antifungal agent ketoconazole. This study identifies a new metabolic pathway in this important human pathogen that may be of utility in treating P. aeruginosa infections.  相似文献   

20.
The purpose of this study was to evaluate and compare the use of liquid and solid Murashige and Skoog (MS) medium in different culture vessels for mass production of Catharanthus roseus, an important source of anticancerous compounds, vincristine and vinblastine. Three media conditions i.e. agar-solidified medium (S), liquid medium in agitated conical flask (L) and growtek bioreactor (B) were used. Rapid propagation was achieved through in vitro somatic embryogenesis pathway. The process of embryogenesis has been categorized into induction, proliferation, maturation and germination stages. All in vitro embryogenesis stages were conducted by withdrawing spent liquid medium and by adding fresh MS medium. In optimized 4.52 μM 2,4-D added MS, the callus biomass growth was low in solid (1.65 g) compared to liquid medium in agitated conical flask (1.95 g) and in bioreactor (2.11 g). The number of normal somatic embryos was more in solid medium (99.75/50 mg of callus mass) compared to liquid medium used in conical flask (83.25/callus mass) and growtek bioreactor (84.88/callus mass). The in vitro raised embryos maturated in GA3 (2.60 μM) added medium; and in bioreactor the embryo growth was high, a maximum length of 9.82 mm was observed at the end of four weeks. These embryos germinated into seedlings in BAP (2.22 μM) added medium and the embryo germination ability was more (59.41%) in bioreactor compared to liquid medium in conical flask (55.5%). Shoot length (11.25 mm) was also high in bioreactor compared to agitated conical flask. The liquid medium used in agitated conical flask and bioreactor increased seedling production efficiency, at the same time it also reduced plant recovery time. The embryo generated plants grew normally in outdoor conditions. The exploitation of medium to large culture vessel or bioreactor may make the process more efficient in getting large number of Catharanthus plant as it is the only source of anti-cancerous alkaloids, vincristine and vinblastine.Abbreviations: BA, N6-benzyladenine; 2,4-D, 2,4-Dichlorophenoxyacetic acid; GA3, gibberellic acid; NAA, naphthalene acetic acid; MS, Murashige and Skoog (1962) medium; S, agar-solidified medium; L, liquid medium in agitated conical flask; B, growtek bioreactor  相似文献   

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