共查询到20条相似文献,搜索用时 31 毫秒
1.
《Journal of Molecular Catalysis .B, Enzymatic》2011,69(3-4):256-261
Crosslinking of enzyme aggregates is a promising method for enzyme immobilization. In this work, crosslinked enzyme coaggregates of Serratia marcescens lipase with polyethyleneimine (CLECAs-SML-PEI) were prepared using polyethyleneimine (PEI) as coprecipitant and glutaraldehyde as crosslinking reagent. The crude lipase solution at a low protein concentration (0.1 mg/ml), with PEI at a mass ratio of 3:1 (PEI/protein, w/w), was found to be most adequate for the coprecipitation of SML. After crosslinking of the coaggregate of SML-PEI with 0.2% (w/v) glutaraldehyde under ambient temperature, over 70% of the total lipase activity was recovered. Compared with the free SML, the optimum temperature of the CLECAs-SML-PEI was enhanced from 50 °C to 60 °C and its thermal stability was also significantly improved. CLECAs-SML-PEI showed excellent operational stability in repeated use in aqueous–toluene biphasic system for asymmetric hydrolysis of trans-3-(4′-methoxyphenyl)glycidic acid methyl ester (MPGM), without significant inactivation after 10 rounds of repeated use. 相似文献
2.
《Enzyme and microbial technology》2008,42(6-7):828-834
An alginate lyase with high specific enzyme activity was purified from Vibrio sp. YKW-34, which was newly isolated from turban shell gut. The alginate lyase was purified by in order of ion exchange, hydrophobic and gel filtration chromatographies to homogeneity with a recovery of 7% and a fold of 25. This alginate lyase was composed of a single polypeptide chain with molecular mass of 60 kDa and isoelectric point of 5.5–5.7. The optimal pH and temperature for alginate lyase activity were pH 7.0 and 40 °C, respectively. The alginate lyase was stable over pH 7.0–10.0 and at temperature below 50 °C. The alginate lyase had substrate specificity for both poly-guluronate and poly-mannuronate units. The kcat/Km value for alginate (heterotype) was 1.7 × 106 s−1 M−1. The enzyme activity was completely lost by dialysis and restored by addition of Na+ or K+. The optimal activity exhibited in 0.1 M of Na+ or K+. This enzyme was resistant to denaturing reagents (SDS and urea), reducing reagents (β-mercaptoethanol and DTT) and chelating reagents (EGTA and EDTA). 相似文献
3.
Jia Zhou Yong-Ming Lu Li-Qun Deng Zhong-Zhen Zhou Wen-Hua Chen 《Bioorganic & medicinal chemistry letters》2013,23(11):3145-3148
Three bis(choloyl) conjugates bearing a rigid p-phenylenediamine/p-bis(aminomethyl)benzene linker and amino/acetamido groups were synthesized, and fully characterized on the basis of 1H NMR, ESI-MS and HRMS. Their ionophoric activities were investigated by means of pH discharge assay. The results indicate that these conjugates exhibit potent ionophoric activities across egg-yolk l-α-phosphatidylcholine (EYPC)-based liposomal membranes, via a cation/proton antiport mechanism. They show moderate ion selectivity among alkali metal ions. Of the three conjugates, the ones having amino groups transport alkali metal ions in the order of Na+ > Li+ > K+ ≈ Rb+ ≈ Cs+, whereas the one having acetamido groups functions in the order of Li+ > Na+ > K+ ≈ Rb+ ≈ Cs+. 相似文献
4.
《Process Biochemistry》2010,45(7):1088-1093
An extracellular thermostable α-galactosidase from Aspergillus parasiticus MTCC-2796 was purified 16.59-fold by precipitation with acetone, followed by sequential column chromatography with DEAE-Sephadex A-50 and Sephadex G-100. The purified enzyme was homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). It was found to be a monomeric protein with a molecular weight of about 67.5 kDa. The purified enzyme showed optimum activity against o-nitrophenyl-α-d-galactopyranoside (oNPG) at pH 5.0 and a temperature of 50 °C. The enzyme was thermostable, showing complete activity even after heating at 65 °C for 30 min. The enzyme showed strict substrate specificity for α-galactosides and hydrolyzed oNPG (Km = 0.83 mM), melibiose (Km = 2.48 mM) and raffinose (Km = 5.83 mM). Among metal ions and reagents tested, Ca2+ and K+ enhanced the enzymatic activity, but Mg2+, Mn2+, ethylenediaminetetraacetic acid (EDTA) and 2-mercaptoethanol showed no effect, while Ag+, Hg2+ and Co2+ strongly inhibited the activity of the enzyme. The enzyme catalyzed the transglycosylation reaction for the synthesis of melibiose. 相似文献
5.
Babu Joseph Nitisha Shrivastava Pramod W. Ramteke 《Journal of Genetic Engineering and Biotechnology》2012,10(1):137-144
A psychrophilic bacterium producing cold-active lipase upon growth at low temperature was isolated from the soil samples of Gangotri glacier and identified as Microbacterium luteolum. The bacterial strain produced maximum lipase at 15 °C, at a pH of 8.0. Beef extract served as the best organic nitrogen source and ammonium nitrate as inorganic for maximum lipase production. Castor oil served as an inducer and glucose served as an additional carbon source for production of cold-active lipase. Ferric chloride as additional mineral salt in the medium, highly influenced the lipase production with an activity of 8.01 U ml?1. The cold-active lipase was purified to 35.64-fold by DEAE-cellulose column chromatography. It showed maximum activity at 5 °C and thermostability up to 35 °C. The purified lipase was stable between pH 5 and 9 and the optimal pH for enzymatic hydrolysis was 8.0. Lipase activity was stimulated in presence of all the solvents (5%) tested except with acetonitrile. Lipase activity was inhibited in presence of Mn2+, Cu2+, and Hg2+; whereas Fe+, Na+ did not have any inhibitory effect on the enzyme activity. The purified lipase was stable in the presence of SDS; however, EDTA and dithiothreitol inhibited enzyme activity. Presence of Ca2+ along with inhibitors stabilized lipase activity. The cold active lipase thus exhibiting activity and stability at a low temperature and alkaline pH appears to be practically useful in industrial applications especially in detergent formulations. 相似文献
6.
Christopher Roberge Deborah Amos David Pollard Paul Devine 《Journal of Molecular Catalysis .B, Enzymatic》2009,56(1):41-45
A cross-linked enzyme aggregate (CLEA®) of chloroperoxidase (CPO) was created that exhibited greatly improved stability in the presence of hydrogen peroxide concentrations as high as 1.2 M. The CPO-CLEA was generated by oxidizing the protein with sodium periodate and precipitating and cross-linking with ammonium sulfate and sodium borohydride. CLEA® production parameters, including the concentrations of these three reagents, were optimized to maximize the activity of the biocatalyst in oxidizing 7-azaindole to 7-azaoxindole. Additionally, the in situ production of the CLEA® was demonstrated, resulting in a process for converting >90% of 5 g/l 7-azaindole in <1 h while requiring neither gradual peroxide addition nor immobilized enzyme isolation. 相似文献
7.
《Process Biochemistry》2010,45(9):1563-1569
A soil-isolated bacterium (strain B4) was identified as a species of Bordetella and deposited with the China General Microbiological Culture Collection (code, CGMCC 2229). The bacterium grew in a mineral medium, on cholesterol as a sole source of carbon and energy. Only one metabolite of cholesterol was accumulated in detectable amounts during the strain growth. It was identified as 4-cholesten-3-one. Cholesterol oxidase (COD) (EC 1.1.3.6), which catalyzes cholesterol into this metabolite, was evidenced from the strain. The conditions of the bacterium growth were optimized for extracellular enzyme production, which then reached around 1700 UL−1 within 24 h culturing. The enzyme was purified from the spent medium of the strain to homogeneity on SDS-PAGE, and characterized. Its molecular mass, as estimated by this technique, was 55 kDa. COD showed an optimum activity at pH 7.0. It was completely stable at pH 5.0 and 4 °C for 48 h, and retained 80% at least of its initial activity at pH 4.0 or at a pH of 6.0–10.0. The optimum temperature for its reaction was 37 °C. The thermal stability of COD was appreciable, as 90% or 80% of its initial activity was recovered after 1 h or 2 h incubation at 50 °C. Ag+ or Hg+ at 1 mM, was inhibitor of COD activity, while Cu2+, at the same concentration, was activator. The COD Km, determined at 37 °C and pH 7.0, was 0.556 mM. The enzyme was stable at pH 7.0 and 37 °C during 24 h mechanical shaking in the presence of 33% (v/v) of either of the solvents, dimethylsulfoxide, ethyl acetate, butanol, chloroform, benzene, xylene or cyclohexane. 相似文献
8.
In this study, polyurethane foam (PUF) was used for immobilization of Yarrowia lipolytica lipase Lip2 via polyethyleneimine (PEI) coating and glutaraldehyde (GA) coupling. The activity of immobilized lipases was found to depend upon the size of the PEI polymers and the way of GA treatment, with best results obtained for covalent-bind enzyme on glutaraldehyde activated PEI-PUF (MW 70,000 Da), which was 1.7 time greater activity compared to the same enzyme immobilized without PEI and GA. Kinetic analysis shows the hydrolytic activity of both free and immobilized lipases on triolein substrate can be described by Michaelis–Menten model. The Km for the immobilized and free lipases on PEI-coated PUF was 58.9 and 9.73 mM, respectively. The Vmax values of free and immobilized enzymes on PEI-coated PUF were calculated as 102 and 48.6 U/mg enzyme, respectively. Thermal stability for the immobilization preparations was enhanced compared with that for free preparations. At 50 °C, the free enzyme lost most of its initial activity after a 30 min of heat treatment, while the immobilized enzymes showed significant resistance to thermal inactivation (retaining about 70% of its initial activity). Finally, the immobilized lipase was used for the production of lauryl laurate in hexane medium. Lipase immobilization on the PEI support exhibited a significantly improved operational stability in esterification system. After re-use in 30 successive batches, a high ester yield (88%) was maintained. These results indicate that PEI, a polymeric bed, could not only bridge support and immobilized enzymes but also create a favorable micro-environment for lipase. This study provides a simple, efficient protocol for the immobilization of Y. lipolytica lipase Lip2 using PUF as a cheap and effective material. 相似文献
9.
《Biochimica et Biophysica Acta - Proteins and Proteomics》2007,1774(12):1500-1507
Salts inhibit the activity of sweet almond β-glucosidase. For cations (Cl− salts) the effectiveness follows the series: Cu+2, Fe+2 > Zn+2 > Li+ > Ca+2 > Mg+2 > Cs+ > NH4+ > Rb+ > K+ > Na+ and for anions (Na+ salts) the series is: I− > ClO4− > −SCN > Br− ≈ NO3− > Cl− ≈ −OAc > F− ≈ SO4− 2. The activity of the enzyme, like that of most glycohydrolases, depends on a deprotonated carboxylate (nucleophile) and a protonated carboxylic acid for optimal activity. The resulting pH-profile of kcat/Km for the β-glucosidase-catalyzed hydrolysis of p-nitrophenyl glucoside is characterized by a width at half height that is strongly sensitive to the nature and concentration of the salt. Most of the inhibition is due to a shift in the enzymic pKas and not to an effect on the pH-independent second-order rate constant, (kcat/Km)lim. For example, as the NaCl concentration is increased from 0.01 M to 1.0 M the apparent pKa1 increases (from 3.7 to 4.9) and the apparent pKa2 decreases (from 7.2 to 5.9). With p-nitrophenyl glucoside, the value of the pH-independent (kcat/Km)lim (= 9 × 104 M− 1 s− 1) is reduced by less than 4% as the NaCl concentration is increased. There is a similar shift in the pKas when the LiCl concentration is increased to 1.0 M. The results of these salt-induced pKa shifts rule out a significant contribution of reverse protonation to the catalytic efficiency of the enzyme. At low salt concentration, the fraction of the catalytically active monoprotonated enzyme in the reverse protonated form (i.e., proton on the group with a pKa of 3.7 and dissociated from the group with a pKa of 7.2) is very small (≈ 0.03%). At higher salt concentrations, where the two pKas become closer, the fraction of the monoprotonated enzyme in the reverse protonated form increases over 300-fold. However, there is no increase in the intrinsic reactivity, (kcat/Km)lim, of the monoprotonated species. For other enzymes which may show such salt-induced pKa shifts, this provides a convenient test for the role of reverse protonation. 相似文献
10.
Lars H. Wegner 《生物化学与生物物理学报:生物膜》2013,1828(8):1973-1981
Cation selectivity of the cellular membrane of tobacco culture cells (cell line ‘bright yellow-2’) exposed to pulsed electric fields in the millisecond range was investigated. The whole cell configuration of the patch clamp technique was established on protoplasts prepared from these cells. Ion selectivity of the electroporated membrane was investigated by measuring the reversal potential of currents passing through field-induced pores. To this end the membrane was hyper- or depolarized for 10 ms (prepulse); subsequently the voltage was driven to opposite polarity at a constant rate (+ 40 or ? 40 mV/ms, respectively). The experiment was started by polarizing the membrane to moderately negative or positive voltages (prepulse potential ± 150 mV) that would not induce pore formation. Subsequently, an extended voltage range was scanned in the porated state of the membrane (prepulse potential ± 600 mV). IV curves in the porated and the non-porated state (obtained at the same prepulse polarity) were superimposed to determine the voltage at which both curves intersected (‘Intersection potential’). Using a modified version of the Goldmann–Hodgkin–Katz equation relative permeabilities to Ca2 + and various monovalent alkali and organic cations were calculated. Pores were found to be fairly cation selective, with a selectivity sequence determined to be Ca2 + > Li+ > Rb+ ≈ K+ ≈ Na+ > TEA+ ≈ TBA+ > Cl?. Relative permeability to monovalent cations was inversely related to the ionic diameter. By fitting a formalism suggested by Dwyer at al. (J. Gen. Physiol. 75 (1980), 469–492) the effective average diameter of field induced pores was estimated to be about 1.8 nm. Implications of these results for biotechnology and electroporation theory are discussed. 相似文献
11.
Lilla Svastits-Dücső Quang D. Nguyen Dominika Dóra Lefler Judit M. Rezessy-Szabó 《Enzyme and microbial technology》2009,45(5):367-371
Thermophilic fungus Thermomyces lanuginosus CBS 395.62/b strain is able to grow and synthesise extracellular α-galactosidase in media containing galactomannan such as locust bean gum (LBG) or guar gum (GG). Production of extracellular α-galactosidase was enhanced from 1.2 U/mL to 4–6 U/mL meaning about 3–5 times increase by optimisation of medium composition. This enzyme was purified to homogeneity by partial precipitation with 2-propanol and different liquid chromatographical steps. The developed purification protocol yielded 22% of enzyme activity with 900 purified fold. Molecular mass of the purified α-galactosidase enzyme was estimated to be 53 kDa. Maximal catalytic activity of the enzyme was obtained in the acidic pH range between pH 4.6 and 4.8 and in the temperature range 60–66 °C. More than 95% of enzyme activity was remaining after 1-day incubation at 70 °C and on pH in the range from 4.0 to 7.0. The enzyme activity was significantly stimulated by Mg2+, Mn2+ and K+ ions, while considerably inhibited by the presence of Ca2+, Ag+ and Hg2+. 相似文献
12.
The SDG-β-d-glucosidase that hydrolyzes the glucopyranoside bond of secoisolariciresinol diglucoside (SDG) to release secoisolariciresinol (SECO) was isolated from Aspergillus oryzae 39 strain and the enzyme was purified and characterized. The enzyme was purified to one spot in SDS polyacrylamide gel electrophoresis, and its molecular weight was about 64.9 kDa. The optimum temperature of the SDG-β-d-glucosidase was 40 °C, and the optimum pH was 5.0. The SDG-β-d-glucosidase was stable at less than 65 °C, and pH 4.0–6.0. Ca2+, K+, Mg2+ and Na+ ions have no significant effect on enzyme activity, Zn2+ and Cu2+ ions have weakly effect on enzyme activity, but Fe3+ ion inhibits enzyme activity strongly. The Km value of SDG-β-d-glucosidase was 0.14 mM for SDG. 相似文献
13.
《Neurochemistry international》2009,54(6-8):338-345
[3H]noradrenaline ([3H]NA) released from sympathetic nerves in the isolated main pulmonary artery of the rabbit was measured in response to field stimulation (2 Hz, 1 ms, 60 V for 3 min) in the presence of uptake blockers (cocaine, 3 × 10−5 M and corticosterone, 5 × 10−5 M). The [3H]NA-release was fully blocked by the combined application of the selective and irreversible ‘N-type’ voltage-sensitive Ca2+-channel (VSCC)-blocker ω-conotoxin (ω-CgTx) GVIA (10−8 M) and the ‘non-selective’ VSCC-blocker aminoglycoside antibiotic neomycin (3 × 10−3 M). Na+-loading (Na+-pump inhibition by K+-free perfusion) was required to elicit further NA-release after blockade of VSCCs (ω-CgTx GVIA + neomycin). In K+-free solution, in the absence of functioning VSCCs (ω-CgTx GVIA + neomycin), the fast Na+-channel activator veratridine (10−5 M) further potentiated the nerve-evoked release of [3H]NA. This NA-release was significantly inhibited by KB-R7943, and fully blocked by . However, Li+-substitution was surprisingly ineffective. The non-selective K+-channel blocker 4-aminopyridine (4-AP, 10−4 M) also further potentiated the nerve-evoked release of NA in K+-free solution. This potentiated release was concentration-dependently inhibited by KB-R7943, significantly inhibited by Li+-substitution and abolished by .It is concluded that in Na+-loaded sympathetic nerves, in which the VSCCs are blocked, the reverse Na+/Ca2+-exchange-mediated Ca2+-entry is responsible for transmitter release on nerve-stimulation. Theoretically we suppose that the fast Na+-channel and the exchanger proteins are close to the vesicle docking sites. 相似文献
14.
《Biochimica et Biophysica Acta (BBA)/General Subjects》2016,1860(3):569-575
BackgroundFluoroquinolones target bacterial type IIA topoisomerases, DNA gyrase and topoisomerase IV (Topo IV). Fluoroquinolones trap a topoisomerase–DNA covalent complex as a topoisomerase–fluoroquinolone–DNA ternary complex and ternary complex formation is critical for their cytotoxicity. A divalent metal ion is required for type IIA topoisomerase-catalyzed strand breakage and religation reactions. Recent studies have suggested that type IIA topoisomerases use two metal ions, one structural and one catalytic, to carry out the strand breakage reaction.MethodsWe conducted a series of DNA cleavage assays to examine the effects of fluoroquinolones and quinazolinediones on Mg2 +-, Mn2 +-, or Ca2 +-supported DNA cleavage activity of Escherichia coli Topo IV.ResultsIn the absence of any drug, 20–30 mM Mg2 + was required for the maximum levels of the DNA cleavage activity of Topo IV, whereas approximately 1 mM of either Mn2 + or Ca2 + was sufficient to support the maximum levels of the DNA cleavage activity of Topo IV. Fluoroquinolones promoted the Topo IV-catalyzed strand breakage reaction at low Mg2 + concentrations where Topo IV alone could not efficiently cleave DNA.Conclusions and general significanceAt low Mg2 + concentrations, fluoroquinolones may stimulate the Topo IV-catalyzed strand breakage reaction by promoting Mg2 + binding to metal binding site B through the structural distortion in DNA. As Mg2 + concentration increases, fluoroquinolones may inhibit the religation reaction by either stabilizing Mg2 + at site B or inhibition the binding of Mg2 + to site A. This study provides a molecular basis of how fluoroquinolones stimulate the Topo IV-catalyzed strand breakage reaction by modulating Mg2 + binding. 相似文献
15.
This work is a report of the characterization of an alkaline lipolytic enzyme isolated from Bacillus subtilis DR8806. The extracellular extract was concentrated using ammonium sulfate, and ultrafiltration. The active enzyme was purified by Q-sepharose ion exchange chromatography. The molecular mass of the enzyme was estimated to be 60.25 kDa based on SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis). The optimum pH and temperature of this enzyme were observed to be 8.0 and 50 °C, respectively. The enzyme exhibited a half-life of 72 min at its optimum temperature. It was stable in the presence of metal ions (10 mM) such as Ca2+, K+ and Na+, whereas Cu2+, Fe2+, Zn2+, Mn2+, Co2+, Mg2+ and Hg2+ were found to have inhibitory effects. However, the enzyme activity was not affected significantly by 1% Triton X-100. The study of substrate specificity showed that the purified enzyme has a preferential specificity for small ester of p-nitrophenyl acetate (C2), and it was the most efficiently hydrolyzed substrate as compared to the other esters. The kinetic parameters showed that the enzyme has Km of 4.2 mM and Vmax of 151 μmol min−1 mg−1 for p-nitrophenyl acetate. The hydrolysis rates of the fluorescence substrates were increased in the presence of the purified enzyme. Regarding the features of the enzyme, it may be utilized as a novel candidate for industrial applications. 相似文献
16.
Li Shao Tong Xu Xiutao Zheng Dandan Shao Haitao Zhang Huiwen Chen Zhenglai Zhang Mingxue Yan Heba Abdel-Motaal Juquan Jiang 《Journal of molecular biology》2021,433(2):166730
Na+/H+ antiporters are a category of ubiquitous transmembrane proteins with various important physiological roles in almost all living organisms ranging from bacteria to humans. However, the knowledge of novel Na+/H+ antiporters remains to be broadened, and the functional roles of oligomerization in these antiporters have not yet been thoroughly understood. Here, we reported functional analysis of an unknown transmembrane protein composed of 103 amino acid residues. This protein was found to function as a Na+(Li+, K+)/H+ antiporter. To the best of our knowledge, this antiporter is the minimal one of known Na+/H+ antiporters and thus designated as NhaM to represent the minimal Na+/H+ antiporter. NhaM and its homologs have not yet been classified into any protein family. Based on phylogenetic analysis and protein alignment, we propose NhaM and its homologs to constitute a novel transporter family designated as NhaM family. More importantly, we found that NhaM is assembled with parallel protomers into a homo-oligomer and oligomerization is vital for the function of this antiporter. This implies that NhaM may adopt and require an oligomer structure for its normal function to create a similar X-shaped structure to that of the NhaA fold. Taken together, current findings not only present the proposal of a novel transporter family but also positively contribute to the functional roles of oligomerization in Na+/H+ antiporters. 相似文献
17.
《生物化学与生物物理学报:生物膜》2015,1848(2):488-495
The palmitate/Ca2 +-induced (Pal/Ca2 +) pore, which is formed due to the unique feature of long-chain saturated fatty acids to bind Ca2 + with high affinity, has been shown to play an important role in the physiology of mitochondria. The present study demonstrates that the efflux of Ca2 + from rat liver mitochondria induced by ruthenium red, an inhibitor of the energy-dependent Ca2 + influx, seems to be partly due to the opening of Pal/Ca2 + pores. Exogenous Pal stimulates the efflux. Measurements of pH showed that the Ca2 +-induced alkalization of the mitochondrial matrix increased in the presence of Pal. The influx of Ca2 + (Sr2 +) also induced an outflow of K+ followed by the reuptake of the ion by mitochondria. The outflow was not affected by a K+/H+ exchange blocker, and the reuptake was prevented by an ATP-dependent K+ channel inhibitor. It was also shown that the addition of Sr2 + to mitochondria under hypotonic conditions was accompanied by reversible cyclic changes in the membrane potential, the concentrations of Sr2 + and K+ and the respiratory rate. The cyclic changes were effectively suppressed by the inhibitors of Ca2 +-dependent phospholipase A2, and a new Sr2 + cycle could only be initiated after the previous cycle was finished, indicating a refractory period in the mitochondrial sensitivity to Sr2 +. All of the Ca2 +- and Sr2 +-induced effects were observed in the presence of cyclosporin A. This paper discusses a possible role of Pal/Ca2 + pores in the maintenance of cell ion homeostasis. 相似文献
18.
Nastia Vasileva Tzonka Godjevargova Danka Ivanova Katya Gabrovska 《International journal of biological macromolecules》2009,44(2):190-194
A non-modified and modified with NaOH and ethylenediamine ultrafiltration membranes prepared from AN copolymer have been used as carriers for the immobilization of horseradish peroxidase (HRP) enzyme. The amount of bound protein onto the membranes and the activity of the immobilized enzyme have been investigated as well as the pH and thermal optimum, and the thermal stability of the free and immobilized HRP. The experiments have proved that the modified membrane is a better support for the immobilization of HRP enzyme. The latter has shown a greater thermal stability than the free enzyme.A possible application has been studied for reducing phenol concentration in water solutions through oxidation of phenol by hydrogen peroxide, in the presence of free and immobilized HRP enzyme on modified AN copolymer membranes. A higher degree of the phenol oxidation has been observed in the presence of the immobilized enzyme. A total removal of phenol has been achieved in the presence of immobilized HRP at concentration of the hydrogen peroxide 0.5 mmol L?1 and concentration of the phenol in the model solutions within the interval 5–40 mg L?1. A high degree of phenol oxidation (95.4%) has been achieved in phenol solution with 100 mg L?1 concentration in the presence of hydrogen peroxide and immobilized HRP, which demonstrates the promising opportunity of using the enzyme for bioremediation of waste waters, containing phenol.The immobilized HRP has shown good operational stability. Deactivation of the immobilized enzyme to 50% of the initial activity has been observed after the 20th day of the enzyme operation. 相似文献
19.
A simple and convenient method was proposed in this paper to develop a flow-through enzymatic micro-reactor made from polytetrafluoroethylene (PTFE). It consisted of the polydopamine layer (functioned as a primer) and layer by layer (LBL) coatings composed of polyethylenimine (PEI) and lipase. The multiple deposition of PEI and lipase was the key factor of increasing the enzyme loading on microreactor. After 8 PEI/lipase layers, enzyme loading on the inner surface of 5-m microchannel reached a maximum (350 μg to 400 μg), compared with approximately 20 μg in single layer. Microreactor with higher enzyme loading was successfully applied on transesterification of soybean oil for effective fatty acid methyl ester (FAME, biodiesel) production. A 95.2% conversion rate of biodiesel can be achieved in 53 min under optimized conditions, instead of a couple of hours in the traditional batch reaction. 相似文献
20.
Teresa Cunha-Oliveira Lisbeth Silva Ana Maria Silva António J. Moreno Catarina R. Oliveira Maria S. Santos 《Life sciences》2013,92(24-26):1157-1164
AimsCocaine and heroin are frequently co-abused in a combination known as speedball. Despite the relevance of the liver in the metabolism and detoxification of these drugs, little is known about the impact of speedball on liver function.Main methodsIn this work, we evaluated the effects of cocaine, morphine and morphine + cocaine (Mor + Coc) combination (1:1) in isolated rat liver mitochondria, upon glutamate/malate or succinate energization, on bioenergetics and oxidative stress-related parameters by using Clark O2, Ca2 +, TPP+ and pH electrodes and by measuring thiobarbituric acid reactive substances (TBARS) and H2O2 production.Key findingsCocaine and Mor + Coc at the higher concentrations (1 mM) similarly increased O2 consumption at state 2, state 4 and state oligomycin. In these conditions, maximum respiration was decreased only upon glutamate/malate energization, suggesting an involvement of complex I. Morphine (1 mM) only increased state 2 respiration. Cocaine and Mor + Coc induced a similar decrease in maximum mitochondrial membrane potential and in ADP-induced depolarization, whereas morphine had no effect. The drugs and their combination similarly decreased mitochondrial ATPase activity and had no effect on Ca2 +-induced permeability transition. Morphine and Mor + Coc prevented lipid peroxidation, since in these conditions there was a decrease in O2 consumption and in TBARS upon ADP/Fe2 + stimulus, and a decrease in H2O2 formation, suggesting an antioxidant effect. Interestingly, heroin did not share morphine antioxidant properties.SignificanceOur results show that the sequential direct exposure of liver mitochondria to morphine and cocaine does not alter the effects observed in the presence of each drug alone. 相似文献