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1.
B.R. MOHAPATRA, R.K. SANI AND U.C. BANERJEE. 1995. The bacterial flora associated with an intertidal marine alga ( Sargassum sp.) were screened for the presence of extracellular L-asparaginase; one out of five Bacillus strains was found positive. The maximum L-asparaginase activity was found at 37°C and pH 8.0. The optimum NaCl concentration for enzyme activity was found to be 2% (w/v). The enzyme activity was not affected by the addition of different metal ions (Ca2+ , Co2+ , Fe2+ , Mg2+ and Ni2+ ) at 10 mmol 1-1 , but was strongly inhibited by EDTA. 相似文献
2.
Indispensability of Iron for the Growth of Cultured Chick Cells 总被引:1,自引:0,他引:1
KOJI SAITO YASUKO HAGIWARA TAKAYUKI HASEGAWA EIJIRO OZAWA 《Development, growth & differentiation》1982,24(6):571-580
In order to clarify the role of iron in the growth promoting effect of transferrin (Tf), the effects of the following substances were examined in cultured chick skeletal myogenic cells: transition metal ions (Fe2+ , Fe3+ , Cr3+ , Cu2+ , Mn2+ , Co2+ , Cd2+ , Zn2+ and Ni2+ ), Tf complexes with these metals and metal-free apoTf.
The cells did not grow well when incubated in a culture medium composed of Eagle's minimum essential medium and horse serum. But they grew well in the presence of Fe2+ or Fe3+ (10–100 μM) or iron-bound Tf (10–500 nM) in the medium. None of the transition metal ions other than iron was effective. Neither apoTf nor Tf complexes with these metals showed the growth promoting effect. The generality of the requirement of iron for cell growth was ascertained in the primary culture of other types of chick embryonic cells: fibroblasts, cardiac myocytes, retinal pigment cells and spinal nerve cells.
The results show that iron is one of the indispensable substances for cell growth and suggest that Tf protein plays a role in facilitating the transport of iron into the cells. 相似文献
The cells did not grow well when incubated in a culture medium composed of Eagle's minimum essential medium and horse serum. But they grew well in the presence of Fe
The results show that iron is one of the indispensable substances for cell growth and suggest that Tf protein plays a role in facilitating the transport of iron into the cells. 相似文献
3.
The uptake of Cd2+ by excised roots of Tamarix aphylla (L.) Karst, was investigated using roots of hydroponically grown plants. The concentration isotherm of Cd2+ uptake approached saturation with a single phase hyperbola. The time course of Cd2+ absorption was generally hyperbolic, with an apparent linear section between 2 and 30 min. The temperature response varied among different temperature ranges: a Q10 of approximately 1.9 was found between 10 and 20°C, but at higher and lower temperatures Q10 values were only 1–1.3. It is concluded that Cd2+ uptake by the roots of T. aphylla at moderate temperatures is mediated by a metabolic process, combined with a passive influx component that becomes dominant at higher and lower temperatures. The distribution of the absorption sites for Cd2+ and for Fe2+ along the roots of T. aphylla was also investigated. Cadmium uptake showed no apparent pattern, whereas a distinct pattern of uptake was observed for Fe2+ , with the highest rates at the root tip. Iron absorption was stimulated in the presence of nutrients, whereas that of Cd2+ was inhibited. Adsorption and absorption of Cd2+ were strongly inhibited by Ca2+ and by Mg2+ , but were unaffected by Fe2+ . Monovalent ions (Na+ , K+ , Li+ ) also reduced Cd2+ absorption, but to a lesser extent than Ca2+ and Mg2+ . Uptake of Cd+ was reduced at lower pH of the medium. The importance of interfering cations for Cd2+ tolerance of T. aphylla is emphasized. 相似文献
4.
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
5.
The in vivo metabolism of D-[U-14 C]glucosamine and the in vitro properties of glucosamine acetyltransferase (EC 2.3.1.3), the first committed enzyme in the metabolism of exogenously supplied D-glucosamine, were studied in coleoptile segments of Avena sativa L. cv. Sole II. D-[U-14 C]glucosamine was taken up by oat coleoptile segments and sequentially metabolised to radioactive N-acetylglucosamine, N-acetylglucosamine 6-P, N-acetylglucosamine 1-P, UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine. In addition, N-acetylglucosamine residues were incorporated into glycoproteins and glycolipids of the cells. All glucosamine acetyltransferase activity was found to be membrane-bound. The enzyme was solubilized by either digitonin or CHAPS. The specificities and the kinetics of the membrane-bound and soluble glucosamine acetyltransferase were determined. The effects of ions, nucleotides, nucleoside diphosphate amino sugars, coenzymes and group-specific chemical probes on the rate of membrane-bound and CHAPS-solubilized enzyme were investigated. Our data indicate that UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine do not exert a feed-back control on the glucosamine acetyltransferase either in vivo or in vitro. Further, some nucleotides and the metal ions Cu2+ , Zn2+ , Fe2+ , Fe3+ and Co2+ affect the activity of the enzyme in vitro. 相似文献
6.
Mechanism of iron uptake by plants 总被引:5,自引:0,他引:5
JOHN C. BROWN 《Plant, cell & environment》1978,1(4):249-257
Abstract. Green plants require a continuous supply of Fe as they grow, because Fe does not not move from the older to the newer leaves. Soils do not lack Fe per se , but it may not be available to plants grown in alkaline soils. Plants are classed 'Fe-efficient' if they respond to Fe-deficiency stress by inducing biochemical reactions that make Fe available in a useful form, and 'Fe-inefficienT' if they do not. Iron uptake induced in response to Fe stress involves release of hydrogen ions and reductants by the root. The lowered pH and presence of reductant at the root zone, along with reduction of Fe3+ to Fe2+ at the root surface, enables Fe2+ to be taken up primarily through the young lateral roots. Ferrous iron is present throughout the protozylem and may or may not have entered the root by a carrier. The root-absorbed Fe2+ is oxidized to Fe3+ at the junction of the protoxylem and the metaxylem, chelated by citrate, and then transported in the metaxylem to the plant top. In the plant, the chemical reactions injuced by Fe-deficiency stress may affect nitrate reductase activity, use of Fe from Fe3+ phosphate and chelating agents, and tolerance to heavy metals. An efficient mechanism for Fe uptake in roots appears to be important for the efficient use of Fe in plant tops. 相似文献
7.
Abstract: The activities mediated by the N -methyl-D-aspartate (NMDA) receptor were studied in cultured rat cerebellar granule cells. Micromolar concentrations of the metal binding compounds, EDTA, cysteine, and histidine, as well as serum albumin strongly potentiated receptor activity in the presence of millimolar concentrations of Ca2+ and Mg2+ . The findings indicated that these agents remove an endogenous metal, probably Zn2+ , which attenuates NMDA receptor-mediated 45 Ca uptake and toxicity. Several added metal ions were therefore tested at low micromolar concentrations. Zn2+ was found to be the most potent inhibitor of NMDA-induced 45 Ca uptake, followed by Cu2+ and Fe2+ . Co2+ , Cd2+ , Fe3+ , and AI3+ had no significant effect, whereas Ni2+ potentiated the 45 Ca uptake but inhibited at much higher concentrations. The potentiating agents that remove the endogenous metal had a particularly dramatic effect in the presence of Mg2+ , the voltage-dependent suppressor of the NMDA receptor. Mg2+ also played an important role in the inhibitory effect of added Zn2+ . Much lower concentrations of Zn2+ were needed to achieve inhibition of NMDA-induced 45 Ca uptake in the presence of Mg2+ . Under a variety of conditions, a very good correlation was found between NMDA receptor-mediated 45 Ca uptake and the magnitude of acute neurotoxicity. 相似文献
8.
The effects of chemicals such as metal ions and typical organic enzyme inhibitors on the activity of deglycosylated β-fructofuranosidases ( P -1 and P -2) from Aureobasidium were observed and compared with those of native enzymes. P -1 and P -2 enzymes became sensitive to metal ions, such as Fe2+ , Co2+ , Ni2+ and Al3+ , after deglycosylation. The enzymes were also inhibited by a sulphydryl reagent (monoiodoacetic acid), a peptide-hydrolysing reagent (hydroxylamine) and chelating reagents (sodium citrate, EDTA and sodium azide) after deglycosylation. The importance of deglycosylation for the determination of the true characteristics of the enzymes against chemicals is discussed. 相似文献
9.
Dai-Eun Sok 《Journal of neurochemistry》1998,70(3):1167-1174
Abstract: Zn2+ -glycerophosphocholine cholinephosphodiesterase, responsible for the conversion of glycerophosphocholine into glycerol and phosphocholine, was inactivated during incubation with ascorbic acid at 38°C. The inclusion of copper ions or Fe2+ accelerated the ascorbate-induced inactivation, with Cu2+ or Cu+ being much more effective than Fe2+ , suggestive of ascorbate-mediated oxidation. Dehydroascorbic acid had no effect on the phosphodiesterase, but H2 O2 inactivated the enzyme in a concentration-dependent manner. Also, the enzyme was inactivated partially by a superoxide anion-generating system but not an HOCl generator. In support of involvement of H2 O2 in the ascorbate action, catalase and superoxide dismutase expressed a complete and a partial protection, respectively. However, hydroxy radical scavengers such as mannitol, benzoate, or dimethyl sulfoxide were incapable of preventing the ascorbate action, excluding the participation of extraneous • OH. Although p -nitrophenylphosphocholine exhibited a modest protection against the ascorbate action, a remarkable protection was expressed by amino acids, especially by histidine. In addition, imidazole, an electron donor, showed a partial protection. Separately, when Cu2+ -induced inactivation of the phosphodiesterase was compared with the ascorbate-mediated one, the protection and pH studies indicate that the mechanism for the ascorbate action is different from that for the Cu2+ action. Here, it is proposed that Zn2+ -glycerophosphocholine cholinephosphodiesterase is one of brain membrane proteins susceptible to oxidative inactivation. 相似文献
10.
Physiological and biochemical modifications induced by Fe-deficiency have been studied in cucumber ( Cucumis sativus L. cv. Marketer) roots, a Strategy I plant that initiates a rapid acidification of the medium and an increase in the electric potential difference when grown under Fe-deficiency. Using the aqueous two-phase partitioning method, a membrane fraction which has the plasmalemma characteristics was purified from roots of plants grown in the absence and in the presence of iron. The plasma membrane vesicles prepared from Fe-deficient plants showed an H+ -ATPase activity (EC 3.6.1.35) that is twice that of the non-deficient control. Furthermore, membranes from Fe-deficient plants showed a higher capacity to reduce Fe3+ -chelates. The difference observed in the reductase activity was small with ferricyanide (only 30%) but was much greater with Fe3 -EDTA and Fe3 -citrate (210 and 250%, respectively). NADH was the preferred electron donor for the reduction of Fe3+ compounds. Fe3+ reduction in plasma membrane from cucumber roots seems to occur with utilisation of superoxide anion, since addition of superoxide dismutase (SOD; EC 1.15.1.1) "in vitro" decreased Fe3+ reduction by 60%.
The response and the difference induced by iron starvation on these two plasma membrane activities together with a possible involvement of O2 in controlling the Fe3+ /Fe2+ ratio in the rhizosphere are discussed. 相似文献
The response and the difference induced by iron starvation on these two plasma membrane activities together with a possible involvement of O
11.
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
12.
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
13.
Abstract: The role of Ca2+ and Mn2+ in Rhodospirillum rubrum grown under different conditions with respect to nitrogen source has been studied. The results show that this phototroph does not have an absolute requirement for these cations. In vitro studies of one of the enzymes operative in the metabolic regulation of nitrogenase in Rsp. rubrum have shown that Mn2+ or Fe2+ is required for activity. This investigation indicates that Mn2+ is not required in vivo for the function of this enzyme, suggesting that either Fe2+ is functional or that the enzyme has other properties when active in the cell. 相似文献
14.
Abstract: Nations were found to inhibit the uptake of L-tryptophan into synaptosomes with a shallow dose-response curve. Almost maximal inhibition was obtained with 10 mM-Na+ . The divalent cations Ca2+ and Mg2+ were shown to be responsible for the increased uptake of L-tryptophan in the absence of Na+ ions. Other divalent cations also promoted tryptophan uptake under this condition (Ca2+ < Mg2+ < Mn2+ < Fe2+ < Zn2+ < Cu2+ ). It was concluded that monovalent chelate complexes were responsible for this enhancing effect. The measured L-tryptophan uptake was the net product of membrane bound and unbound tryptophan. Both bound and unbound tryptophan were increased in the presence of divalent cations. If no divalent cations were added to the incubation medium, Na+ ions decreased the unbound tryptophan but were without effect on bound tryptophan. Under these circumstances D-tryptophan had no effect on binding of the L-isomer and affected the transport of 1.-tryptophan only at very high does (100 x conc. L-tryptophan). These results suggest that I -tryptophan binds to a stereospecific transport carrier located in the synaptosomal membrane and that Na+ ions prevent the translocation of this carrier amino acid complex from the outer to the inner site of the neuronal membrane. 相似文献
15.
Abstract Phosphate interference in the production of cephalosporins by Streptomyces clavuligerus had been associated with repression of expandase (desacetoxycephalosporin C synthetase) and inhibition of both expandase and cyclase (isopenicillin N synthetase). The present work shows that inhibition of enzyme action could be prevented by increasing the Fe2+ added to the cell-free reactions or to resting cells incubated with chloramphenicol. Since excess Fe2+ could not reverse phosphate interference of antibiotic synthesis in complete fermentations, it is clear that the major cause of the phosphate effect in fermentations is phosphate repression, rather than phosphate inhibition caused by Fe2+ deprivation. 相似文献
16.
Zinc is an essential micronutrient, and yet it can be toxic when present in excess. Zinc acquisition and distribution are dependent on tightly controlled transport of Zn2+ ions. Schizosaccharomyces pombe represents a second eukaryotic model to study cellular metal homeostasis. In several ways its micronutrient metabolism is fundamentally different from Saccharomyces cerevisiae . We identified the first Zn2+ -uptake system in S. pombe and named it SpZrt1. Knock-out strains for all three ZIP (Zrt, Irt-like protein) transporters in fission yeast were constructed. Only zrt1 Δ cells were unable to grow at low Zn2+ and showed reduced 65 Zn2+ uptake. Elemental profiles revealed a strong decrease in zinc accumulation. Cd2+ ions inhibited uptake but Fe2+ or Mn2+ did not. Both mRNA abundance and protein amount are tightly regulated. Zrt1 activity is rapidly shut down upon transfer of zinc-deficient cells to zinc-replete conditions. In cells lacking Zhf, a transporter mediating endoplasmic reticulum storage of zinc, this response is about 100-fold more sensitive. Thus, removal of excess of zinc from the cytosol is largely Zhf dependent. Moreover, cells deficient for both transporters are no longer able to adjust to changing external Zn2+ concentrations. Optimal growth is restricted to a narrow range of Zn2+ concentrations, illustrating the fine balance between micronutrient deficiency and toxicity. 相似文献
17.
Obligately anaerobic ruminal bacteria have been found to possess phytase activity, in particular, Selenomonas ruminantium . The phytase activity of S. ruminantium JY35 was produced late in growth and required neither phytate for induction nor phosphate limitation for derepression. The activity was completely cell-associated with a significant fraction extractable by a magnesium chloride solution. Zymogram analysis suggested that the activity was the result of a single gene product of a monomeric nature and approximately 46 kDa in size. The phytase had a temperature optimum of 50–55 °C, but activity dropped off sharply at 60 °C. Phytase activity was optimal over the pH range of 4·0–5·5, and dependent on the nature of the buffer used. Activity was inhibited by citric acid buffer and by the addition of 5 mmol l−1 Fe2+ , Fe3+ , Cu2+ , Zn2+ and Hg2+ . The addition of 5 mmol l–1 Pb2+ to the enzyme assay appeared to enhance activity of the enzyme. 相似文献
18.
Abstract Cytochrome components which participate in the oxidation of nitrite in Nitrobacter winogradskyi have been highly purified and their properties studied in detail. Cytochrome a 1 c 1 is an iron-sulphur molybdoenzyme which has haems a and c and acts as a nitrite-cytochrome c oxidoreductase. Cytochrome c -550 is homologous to eukaryotic cytochrome c and acts as the electron mediator between cytochrome a 1 c 1 and aa 3 -type cytochrome c oxidase. The oxidase is composed of two kinds of subunits, has two molecules of haem a and two atoms of copper in the molecule, and oxidizes actively eukaryotic ferrocytochrome c as well as its own ferrocytochrome c -550. Further, a flavoenzyme has been obtained which has transhydrogenase activity and catalyses reduction of NADP+ with benzylviologen radical. This enzyme may be responsible for production of NADPH in N. winogradskyi . The electron transfer against redox potential from NO2 − to cythochrome c could be pushed through prompt removal by cytochrome aa 3 of H+ formed by the dehydrogenation of NO2 − + H2 O. As cytochrome c in anaerobically kept cell-free extracts is rapidly reduced on addition of NO2 − , a membrane potential does not seem necessary for the reduction of cytochrome c by cytochrome a 1 c 1 with NO2 − in vivo. 相似文献
19.
Characterization of phytochelatin synthase from tomato 总被引:11,自引:0,他引:11
The enzyme that synthesizes Cd-binding phytochelatins (PCs), PC synthase, has been studied in tomato ( Lycopersicon esculentum ) cell cultures and plants. This enzyme transfers γ-GluCys from GSH or PC to either GSH or an existing polymer of (γ-GluCys)n Gly. PC synthase from tomato requires GSH or PCs as substrates but cannot utilise γ-GluCys or GSSG. PC synthase is activated both in vivo and in vitro by a variety of heavy metal ions, including Cd2+ , Ag+ , Cu2+ , Au+ , Zn2+ , Fe2+ , Hg2+ and Pb2+ . In crude protein extracts from tomato cells the enzyme has an apparent Km of 7.7 m M for GSH in the presence of 0.5 m M Cd2+ , and exhibits maximum activity at pH 8.0 and 35°C. PC synthase is present in tomato cells grown in the absence of Cd. The level of enzyme activity is regulated during the cell culture cycle, with the highest activity occurring 3 days after subculture. Cadmium-resistant tomato cells growing in medium containing 6 m M CdCl2 have a 65% increase in PC synthase activity compared to unselected cells. PC synthase is also present in roots and stems of tomato plants, but not in leaves or fruits. The distribution of the enzyme in tomato plants and regulation of PC synthase activity in tomato cells indicate that PC synthase, and PCs, may have additional functions in plant metabolism that are not directly related to the formation of Cd-PC complexes in response to cadmium. 相似文献
20.
A variety of metal microprojectiles are currently used for carrying foreign DNA into living cells via particle-acceleration techniques. While developing a microprojectile-mediated protocol for transforming cells of sugarbeet ( Beta vulgaris L.), formation of a blue precipitate was observed with the indigoqenic substrate 5-bromo-4-chloro-3-indolyl-β-D-glucuronic acid (X-gluc) in the absence of gusA DNA encoding β-D-glucuronidase (GUS). Tungsten microcarriers, but not gold or silicon carbide, proved capable of catalyzing the cleavage of the glucuronide residue from three histochemical substrates evaluated: X-gluc, salmon X-gluc and magenta X-gluc. Indigo-stained sugarbeet cells were observed following bombardment with tungsten in the absence of DNA. Addition of oxidative catalysts to tungsten microcarriers during substrate incubation had no apparent effect on the metal-mediated catalysis. Treatment of microcarriers with Proteinase K and heat ruled out the presence of enzymes. Microbiological evaluation indicated the absence of contaminating microbes. Similarly, metal-catalyzed hydrolysis of the fluorogenic substrate 4-methylumbelliferyl-β-D-glucuronic acid (4-MUG) was observed in the presence of tungsten spheres but not with gold or silicon carbide particles. With this substrate, hydrolysis also occurred with millimolar concentrations of Cu2+ , Fe2+ and Zn2+ ions. Consequently, careful monitoring of DNA-minus controls and avoidance of millimolar concentrations of Cu2+ , Fe2+ and Zn2+ ions are recommended in microprojectile bombardment experiments where transient assays for gusA expression are performed. 相似文献