共查询到20条相似文献,搜索用时 15 毫秒
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Hiroyuki Fujimori Masako Kiyono Kazunori Nobuhara Hidemitsu Pan-Hou 《FEMS microbiology letters》1996,135(2-3):317-321
Abstract To study the physiological role of the red pigments in soil strain Pseudomonas K-62, we isolated a red pigment-deficient white mutant from the soil strain by treatment with mitomycin C and compared the phenotypic properties of the mutant and parent strain. The red pigments, which were classified as one of carotenoids based on their physicochemical properties, were separated into two groups, designated pigment A and B respectively on NH-Chromatorex HPLC.The crude pigments and pigment B which could react with Hg2+ in the wild-type Pseudomonas K-62 and its mercury-resistant plasmid-deficient strain were enhanced by the addition of Hg2+ . The white mutant thus obtained showed a greater sensitivity to Hg2+ than the wild-type reddish strain despite containing the resistant plasmids. The major component in pigment B was identified by mass spectrometric analysis as 1-hydroxy-1-methoxy-1,2, 1',2',7',8'-hexahydro-ψ,ψ-caroten-4-one, a carotenoid monoketone. These results suggested that red pigments, especially pigment B, may account, at least partially, for defense against Hg2+ in the bacterial environments. 相似文献
3.
Abstract Enteropathogenic strains of faecal Escherichia coli produced significantly ( P < 0.01) more maltase than the non-pathogenic strains of the organism. The enzyme was induced by maltose but repressed by glucose and fructose. The maltase was partially purified by ammonium sulphate precipitation, followed by dialysis and gel permeation chromatography. The partially purified maltase had an M r of 144500 and an apparent K m of approx. 7.6 mM for maltose. The enzyme was stimulated by Ca2+ , inhibited by Cu2+ , Hg2+ , Uo2+ , IAA and EDTA, and exhibited optimum activity at pH 6.5 at 30°C. 相似文献
4.
Abstract: The present study addresses the possibility that there are different cocaine-related and mazindol-related binding domains on the dopamine transporter (DAT) that show differential sensitivity to cations. The effects of Zn2+ , Mg2+ , Hg2+ , Li+ , K+ , and Na+ were assessed on the binding of [3 H]mazindol and [3 H]WIN 35,428 to the human (h) DAT expressed in C6 glioma cells under identical conditions for intact cell and membrane assays. The latter were performed at both 0 and 21°C. Zn2+ (30–100 µ M ) stimulated binding of both radioligands to membranes, with a relatively smaller effect for [3 H]mazindol; Mg2+ (0.1–100 µ M ) had no effect; Hg2+ at ∼3 µ M stimulated binding to membranes, with a relatively smaller effect for [3 H]mazindol than [3 H]WIN 35,428 at 0°C, and at 30–100 µ M inhibited both intact cell and membrane binding; Li+ and K+ substitution (30–100 m M ) inhibited binding to membranes more severely than to intact cells; and Na+ substitution was strongly stimulatory. With only a few exceptions, the patterns of ion effects were remarkably similar for both radioligands at both 0 and 21°C, suggesting the involvement of common binding domains on the hDAT impacted similarly by cations. Therefore, if there are different binding domains for WIN 35,428 and mazindol, these are not affected differentially by the cations studied in the present experiments, except for the stimulatory effect of Zn2+ at 0 and 21°C and Hg2+ at 0°C. 相似文献
5.
Microbial formation and transformation of organometallic and organometalloid compounds 总被引:4,自引:0,他引:4
G.M. Gadd 《FEMS microbiology reviews》1993,11(4):297-316
Abstract: Microbial formation and transformation of organometallic and organometalloid compounds comprise significant components of biogeochemical cycles for the metals mercury, lead and tin and the metalloids arsenic, selenium, tellurium and germanium. Methylated derivatives of such elements can arise as a result of chemical and biological mechanisms and this frequently results in altered volatility, solubility, toxicity and mobility. The major microbial methylating agents are methylcobalamin (CH3 CoB12 ), involved in the methylation of mercury, tin and lead, and S -adenosylmethionine (SAM), involved in the methylation of arsenic and selenium. Evidence for the methylation of other toxic metal(loid)s is sparse. Biomethylation may result in metal(loid) detoxification since methylated derivatives may be excreted readily from cells, are often volatile and may be less toxic, e.g. organoarsenicals. However, for mercury, low yields of methylated derivatives and the existence of more efficient resistance mechanisms, e.g. reduction of Hg2+ to Hg0 , suggest a lower significance in detoxification. Bioalkylation has only been characterised in detail for arsenic. Microorganisms can accumulate organometal(loid)s, a phenomenon relevant to toxicant transfer to higher organisms. As well as bioaccumulation, many microorganisms are capable of the degradation and detoxification of organometal(loid) compounds by, e.g. demethylation and dealkylation. Several organometal(loid) transformations have potential for environmental bioremediation. 相似文献
6.
Abstract The carboxylesterases from Proteus vulgaris, Salmonella enterica and Citrobacter amalonaticus were purified 104-, 95- and 120-fold, respectively by chromatography. The enzymes had similar catalytic activities but differed considerably in their inactivation by heat, di-isopropyl fluorophosphate and Cd2+ , Zn2+ , Hg2+ and Cu2+ . Quantitative neutralization of hydrolytic activity with specific immunoglobulins indicated that the three enzymes were antigenically distinct. 相似文献
7.
An acid phosphatase (EC 3.1.3.2.) from the embryonic axes of chickpea seeds ( Cicer arietinum L. cv. Castellana) was purified by ammonium sulphate precipitation, chromatography on Sephacryl S-200 and polyacrylamide gel electrophoresis. The preparation has an apparent molecular weight of 39 kDa, pH optimum for p -nitrophenylphosphate hydrolysis of 5.25, and K m of 0.57 m M . The enzyme hydrolyzed all the mono- and di-phosphorylated sugars tested, but had no effect on ATP, ADP, AMP and phosphoenolpyruvate. Phosphate was a competitive inhibitor. Mg2+ . Ca2+ , Hg2+ , Fe3+ , arsenate, K+ and Zn2+ were inhibitory. Mn2+ , dithiothreitol and EDTA had no effect, and polyamines were activators. 相似文献
8.
Treatment with sucrose induced anthocyanin synthesis and phenylalanine ammonialyase (PAL, EC 4. 3. 1. 5) activity in leaf disks of Indian almond ( Terminalia catappa L. Duthie). Co2+ , an inhibitor of ethylene biosynthesis, inhibited anthocyanin synthesis and PAL activity when given together with sucrose. Ethephon (an exogenous source of ethylene) given along with sucrose, promoted anthocyanin synthesis and PAL activity, but in the presence of Co2+ its effectiveness decreased. In an attempt to understand the inhibitory action of Co2+ in the presence of ethephon, the effect of Co2+ on PAL activity was studied in vitro. A kinetic study showed an uncompetitive type of inhibition of PAL by Co2+ , which was not time dependent. Addition of 2-mercaptoethanol, cysteine or glutathione overcame the in vitro effect of Co2+ , and 2-mercaptoethanol also restored the activity of PAL extracted from Co2+ -treated leaf disks. It is suggested that sulfhydryl group(s) might be involved in the inactivation of PAL by Co2+ . The effects of N-ethylmaleimide (NEM) and HgCl2 (other sulfhydryl reagents) were also studied. Both NEM and Hg2+ competitively inhibited PAL activity in vitro, and the inhibition could be reversed by sulfhydryl compounds. 相似文献
9.
NADP+ -malic enzyme ( l -malate: NADP+ oxidoreductase, decarboxylating EC 1.1.1.40) from pod walls of chickpea was purified 51-fold by ammonium sulphate fractionation, DEAE- cellulose chromatography and gel filtration through Sepharose 4B. The purified enzyme required a divalent cation, either Mn2+ or Mg2+ , for its activity. Km values at pH 7.8 for malate, NADP+ and Mn2+ were 4.0, 0.031 and 0.71 m M , respectively. Mn2+ -dependent activity was inhibited by heavy metal ions such as Cd2+ , Zn2+ , Hg2+ , and to a lesser extent by Pb2+ and Al3+ . Among the organic acids examined, sodium salts of oxalate and oxaloacetate were inhibitory. Kinetics of the reaction mechanism showed sequential binding of malate and NADP+ to the enzyme. Products of reaction, viz. pyruvate, bicarbonate and NADPH, inhibited the enzyme activity. At limiting concentrations of NADP+ , pyruvate and bicarbonate induced a positive cooperative effect by malate. It is proposed that the activity of NADP+ -malic enzyme is controlled by intracellular concentrations of substrates and products. 相似文献
10.
Glucoamylases produced by Aspergillus niger grown on wheat bran in solid cultures were purified. Four different forms, GA I, GA I', GA II and GA III, were found having apparent molecular weights of 112 000, 104 000, 74 000 and 61 000 Da respectively. The enzymes are glycoproteins with a carbohydrate content of 16%, and optimal activity at 60C and pH 4.4. Activity was strongly inhibited by Hg2+ while Mn2+ and Fe2+ were stimulatory. The Km values for the degradation of starch and maltose were 3.5 and 7.8 mg ml-1 , respectively. 相似文献
11.
María Fabiana Drincovich Alberto A. Iglesias Carlos S. Andreo 《Physiologia plantarum》1991,81(4):462-466
The effect of several metal ions on NADP+ -malic enzyme (EC 1.1.1.40) purified from Zea mays L. leaves was studied Mg2+ , Mn2+ , Co2+ and Cd2+ were all active metal cofactors. The malic enzyme from maize has a moderately high intrinsic preference for Mn2+ relative to Mg2+ at pH 7.0 and 8.0 Negative cooperativity detected in the binding of Mg2+ at pH 7.0 and 8.0 and in the binding of Mn2+ at pH 7.0 suggests the existence of at least two binding sites with different affinity. All of the activating metal ions have preference for octahedral coordination geometry and have ionic radii of 0.86–1.09 Å. The ions that act as inhibitors are outside this range and/or are incapable of octahedral coordination. Ba2+ , Sr2+ , Cd2+ , Ca2+ , Be2+ , Ni2+ , Cu2+ , Zn2+ , Co2+ , Hg2+ showed mixed-type inhibition. The reciprocal of their K1 values follow the order of their apparence in the Irving-Williams series of stability that derives in part from size effects. It is suggested that the size of the ions may play a partial role in determining the strength of the metal interaction. 相似文献
12.
Abstract— Three different types of p -nitrophenyl phosphatases (NPPases) were solubilized by deoxycholate treatment from a membrane fraction of bovine cerebral cortex, and their characteristics were determined. Of these three NPPases (acid, Mg2+ -activated, and K+ , Mg2+ -activated), only K-Mg NPPase was stimulated about two-fold by phospholipid and was inhibited by unsaturated neutral lipids and fatty acids. Unlike Na+ -K+ -Mga+ -activated ATPase, the enzyme did not absolutely require phospholipid for its activity, but was similarly thermolabile and was protected by phospholipid from thermal inactivation. Acid NPPase was separable from the other two NPPases by ammonium sulphate fractionation, and partly solubilized by dialysis against ATP-mercaptoethanol solution. Hg2+ inhibited equally all three NPPases, but Ca2+ inhibited only Mg and K-Mg NPPases. Ouabain was effective on K-Mg NPPase alone. 相似文献
13.
Marisa S. Garro Graciela S. de Giori Graciela F. de Valdez G. Oliver 《Journal of applied microbiology》1993,75(5):485-488
α-Galactosidase activity was studied in Lactobacillus fermentum strains. The optimum temperature was found to be 45°C. The enzyme was inactivated at temperatures higher than 55°C, but remained active during storage at low temperatures (0, -30 and -70°C) for 5 months. Enzyme activity was observed within a 5.0–6.5 pH range, while optimum pH was dependent on the particular strain assayed. The addition of Zn2+ to the reaction buffer exerted a slight negative effect upon the activity, while Hg2+ and p -chloromercuribenzoate produced a strong inhibition. These results would indicate the presence of -SH groups in the catalytic site of the enzyme. 相似文献
14.
Studies on the effect of mercury and organomercurial on the growth and nitrogen fixation by mercury-resistant Azotobacter strains 总被引:1,自引:1,他引:0
S. Ghosh P.C. Sadhukhan D.K. Ghosh A.K. Mandal J. Chaudhuri A. Mandal 《Journal of applied microbiology》1996,80(3):319-326
Five nitrogen-fixing Azotobacter strains isolated from agricultural farms in West Bengal, India, were resistant to mercuric ion and organomercurials. Resistance of Hg-resistant bacteria to mercury compounds is mediated by the activities of mercuric reductase and organomercurial lyase in the presence of NADPH and GSH as cofactors. These bacteria showed an extended lag phase in the presence of 10–50 μmol 1-1 HgCl2 . Nitrogen-fixing ability of these isolates was slightly inhibited when the mercuryresistant bacterial cells were preincubated with 10 μmol 1-1 HgCl2 . Acetylene reduction by these bacteria was significantly inhibited (91-97%) by 50 μmol 1-1 HgCl2 . However, when GSH and NADPH were added to the acetylene reduction assay mixture containing 50 μmol 1-1 HgCl2 , only 42–50% inhibition of nitrogenase activity was observed. NADPH and GSH might have a role in suppressing the inhibition of N2 -fixation in the presence of Hg compounds either by assisting Hg-detoxifying enzymes to lower Hg concentration in the assay mixture or by formation of adduct comprising Hg and GSH which is unable to inhibit nitrogen fixation. 相似文献
15.
M. Esther Fárez-Vidal Antonia Fernández-Vivas F. González J.M. Arias 《Journal of applied microbiology》1995,78(1):14-19
M.E.FÁREZ-VIDAL, A. FERNÁNDEZ-VIVAS, F. GONZÁLEZ AND J.M. ARIAS. 1995. The extracellular amylase activity from Myxococcus coralloides D was purified by Sephacryl S-200 gel filtration and by ion-exchange chromatography on DEAE-Sephadex A-25. The molecular weight was estimated by SDS-PAGE and by gel filtration as 22.5 kDa. The optimum temperature was 45°C. The pH range of high activity was between 6.5 and 8.5, with an optimum at pH 8.0. Activity was strongly inhibited by Hg2+ , Zn2+ , Cu2+ , Ag+ , Pb2+ , Fe2+ and Fe3+ , EDTA and glutardialdehyde, but was less affected by Ni2+ and Cd2+ . Li+ , Mg2+ , Ba2+ , Ca2+ , N -ethylmaleimide, carbodiimide and phenyl methyl sulphonyl fluoride had almost no affect. The K m (45°C, pH 8) for starch hydrolysis was 2.0 times 10-3 gl-1 . Comparison of the blue value-reducing curves with the time of appearance of maltose identified the enzyme produced by M. coralloides D as an α-amylase. 相似文献
16.
Adhesion of Salmonella dublin to HEp2 epithelial cells 总被引:1,自引:0,他引:1
Two strains of Salmonella dublin , grown serially in brain heart infusion broth, were motile and produced mannose sensitive (MS) but not mannose resistant (MR) haemagglutinins; grown on phosphate buffered agar, the strains were poorly motile and phenotypically MSHA- MRHA + . In adhesion tests with HEp2 epithelial cells, broth grown bacteria that were motile and MSHA+ MRHA- adhered better than agar grown bacteria that were poorly motile and MSHA- MRHA+ . Thus, in adhesion tests with HEp2 epithelial cells, strains of S. dublin behaved like S. typhimurium strains in that their HEp2 cell adhesiveness was associated with motility and production of MSHA. 相似文献
17.
New insights into the metal specificity of the Pseudomonas aeruginosa pyoverdine–iron uptake pathway
Armelle Braud Françoise Hoegy Karine Jezequel Thierry Lebeau Isabelle J. Schalk 《Environmental microbiology》2009,11(5):1079-1091
Pyoverdine (PvdI) is the major siderophore secreted by Pseudomonas aeruginosa PAOI in order to get access to iron. After being loaded with iron in the extracellular medium, PvdI is transported across the bacterial outer membrane by the transporter, FpvAI. We used the spectral properties of PvdI to show that in addition to Fe3+ , this siderophore also chelates, but with lower efficiencies, all the 16 metals used in our screening. Afterwards, FpvAI at the cell surface binds Ag+ , Al3+ , Cd2+ , Co2+ , Cu2+ , Fe3+ , Ga3+ , Hg2+ , Mn2+ , Ni2+ or Zn2+ in complex with PvdI. We used Inductively Coupled Plasma-Atomic Emission Spectrometry to monitor metal uptake in P. aeruginosa : TonB-dependent uptake, in the presence of PvdI, was only efficient for Fe3+ . Cu2+ , Ga3+ , Mn2+ and Ni2+ were also transported into the cell but with lower uptake rates. The presence of Al3+ , Cu2+ , Ga3+ , Mn2+ , Ni2+ and Zn2+ in the extracellular medium induced PvdI production in P. aeruginosa . All these data allow a better understanding of the behaviour of the PvdI uptake pathway in the presence of metals other than iron: FpvAI at the cell surface has broad metal specificity at the binding stage and it is highly selective for Fe3+ only during the uptake process. 相似文献
18.
The yeast Torulaspora delbrueckii IFO 1255 was selected as the strain fermenting melibiose from 35 strains of Torulaspora species. The strain IFO 1255 produced extracellular and cell-associated forms of α-galactosidase when grown on either melibiose or galactose as the sole carbon source. Most of the enzyme was located outside of the cell membrane: the periplasmic space, or cell walls, or both. α-Galactosidase was purified to homogeneity from the cell-free extract of the strain IFO 1255 by acid treatment and column chromatography on DEAE-Toyopearl 650M and Butyl-Toyopearl 650M. The molecular weight of the purified enzyme was estimated to be 88 000 by SDS-polyacrylamide gel electrophoresis and 530 000 by gel filtration. The enzyme contained 50% of its molecular weight as carbohydrate. Optimum pH and temperature were 4.5–5.5 and 55°C, respectively. The enzyme was inhibited strongly by Ag2+ , Hg2+ and Cu2+ each at 1 mmol 1-1 . The K m (μmol 1-1 ) for p -, o -, m -nitrophenyl α-D-galactopyranoside, melibiose, raffinose and stachyose were 2.8, 1.3, 2.8, 4.2, 170 and 230, respectively, and V max (μmol min-1 mg protein-1 ) for those substrates were 310, 140, 21, 22, 30 and 44, respectively. The properties of α-galactosidase from T. delbrueckii IFO 1255 were similar to those from the related species, Saccharomyces cerevisiae. 相似文献
19.
A procedure for the partial purification of a non-specific alkaline phosphatase (EC 3.1.3.1.) from the embryonic axes of chick-pea seeds is described. Ammonium sulphate precipitation, DEAE-cellulase chromatography, Sephacryl S-200 chroma-tography and polyacrylamide gel electrophoresis are the most important steps. The molecular weight of this non-specific enzyme, as determined by Sephacryl S–200 gel filtration and SDS–polyacrylamide gel electrophoresis, was estimated as being 68 and 78 kDa respectively; the optimum pH for p-nitrophenylphosphate hydrolysis was 7.5, and the Km for this artificial substrate was 0.5 mM. The enzyme catalyzes the hydrolysis of a variety of organic phosphate esters. The best substrates are: phos-phoenolpymvate (Km = 2.4 m M ), NADP+ (Km = 4.0 m M ), 5'-AMP (Km = 4.5 m M ), 5'-ADP (Km = 6.1 m M ) and ribose-5P (Km = 5.8 m M ); but it is unable to hydrolyze 5'-ATP, phosphocreatine and tripolyphosptiate. Phospate was a competitive inhibitor. Zn2+ , K+ , Hg2+ and Mo6+ were strong inhibitors, whereas F− and Ca2+ inhibited weakly; Co2+ and Ni2+ were activators. 相似文献
20.
U. C. Banerjee 《Letters in applied microbiology》1993,17(1):1-3
Curvularia lunata var. aeria was grown on yeast extract, peptone and carboxymethylcellulose (YPC) medium for the production of extracellular rifamycin oxidase. The enzyme was partially purified through a Sephadex G-75 column. The half lives of rifamycin oxidase at 30° and 40°C were 9 d and 100 min, respectively. The activation and deactivation energies of the partially purified enzyme, calculated from Arrhenius plots, were 5.80 and 35.10 kcal mol-1 respectively. The enzyme exhibited a K m (rifamycin B) value of 0.67 mmol l-1 and a V max of 11 μmol h-1 ml. Three metal ions, Fe2+ , Ag+ and Hg2+ , inhibited the enzyme in the 10–20 mmol l-1 metal ion concentration range. Catalytic activity was not affected by the chelating agent, EDTA. 相似文献