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1.
A. Sharma C. L. S. N. Rao B. K. Ball S. K. Hasija 《World journal of microbiology & biotechnology》1996,12(6):615-617
Forty bacterial isolates from the effluents of a gelatin factory (Jabalpur, India) were screened for protease activity and the two most potent producers were identified as Bacillus laterosporus and a Flavobacterium sp. The enzymes of both isolates were optimal at pH 8 and 60°C, with maximum activity after 90 min. The enzyme activity of B. laterosporus was suppressed by Fe2+, Mg2+, Mn2+ and Zn2+ ions but was enhanced by Ba2+ and Ca2+. That of Flavobacterium sp. was suppressed by Mg2+ and Mn2+ ions but enhanced by Ba2+, Ca2+ and Fe2+. The enzyme activity of the former was strongly inhibited by KCN, whereas that of the latter was only slightly inhibited by 8-hydroxyquinoline. 相似文献
2.
Vishal V. Dawkar Umesh U. Jadhav Amar A. Telke Sanjay P. Govindwar 《Biotechnology and Bioprocess Engineering》2009,14(3):361-368
Peroxidase was purified by an ion exchange chromatography followed by gel filtration chromatography from dye degrading Bacillus sp. strain VUS. The optimum pH and temperature of the enzyme activity was 3.0 and 65°C, respectively. This enzyme showed
more activity with n-propanol than other substrates tested viz. xylidine, 3-(3,4-dihydroxy phenyl) Lalanine (L-DOPA), hydroxyquinone, ethanol, indole, and veratrole. Km value of the enzyme
was 0.076 mM towards n-propanol under standard assay conditions. Peroxidase was more active in presence of the metal ions like Li2+, Co2+, K2+, Zn2+, and Cu2+ where as it showed less activity in the presence of Ca2+ and Mn2+. Inhibitors like ethylenediamine tetraacetic acid (EDTA), glutamine, and phenylalanine inhibited the enzyme partially, while
sodium azide (NaN3) completely. The crude as well as the purified peroxidase was able to decolourize different industrial dyes. This enzyme
decolourized various textile dyes and enhanced percent decolourization in the presence of redox mediators. Aniline was the
most effective redox mediator than other mediators tested. Gas chromatography-Mass spectrometry (GC-MS) confirmed the formation
of 7-Acetylamino-4-hydroxy-naphthalene-2-sulphonic acid as the final product of Reactive Orange 16 indicating asymmetric cleavage
of the dye. 相似文献
3.
Loss of substrate, pyruvate, a limitation for enzymatic batch production of (R)-phenylacetylcarbinol (PAC), resulted from two phenomena: temperature dependent non-enzymatic concentration decrease due to the cofactor Mg2+ and formation of by-products, acetaldehyde and acetoin, by pyruvate decarboxylase (PDC). In the absence of enzyme, pyruvate stabilization was achieved by lowering the Mg2+ concentration from 20 to 0.5 mM. With 0.5 mM Mg2+
Rhizopus javanicus and Candida utilis PDC produced similar levels of PAC (49 and 51 g l–1, respectively) in 21 h at 6 °C; however C. utilis PDC formed less by-product from pyruvate and was more stable during biotransformation. The process enhancements regarding Mg2+ concentration and source of PDC resulted in an increase of molar yield (PAC/consumed pyruvate) from 59% (R. javanicus PDC, 20 mM Mg2+) to 74% (R. javanicus PDC, 0.5 mM Mg2+) to 89% (C. utilis PDC, 0.5 mM Mg2+). 相似文献
4.
S. Batista S. Castro M. Ubalde G. Martínez-Drets 《World journal of microbiology & biotechnology》1994,10(3):249-255
Rhizobium tropici, R. leguminosarum bv phaseoli and R. loti each have an active C4-dicarboxylic acid transport system dependent on an energized membrane. Free thiol groups are probably involved at the active site. Since EDTA inhibited succinate transport in R. leguminosarum bv phaseoli and R. loti, divalent cations may participate in the process; the activity was reconstituted by the addition of Ca2+ or Mg2+. However, EDTA had no effect on succinate transport in R. tropici, R. meliloti or R. trifolii strains. Ca2+ or Mg2+ had a similar effect on the growth rates of R. tropici and R. leguminosarum bv phaseoli; R. tropici did not require Ca2+ to grow on minimal medium supplemented with succinate but R. leguminosarum bv phaseoli required either or both of the divalent cations Ca2+ and Mg2+. A R. tropici Mu-dI (lacZ) mutant defective in dicarboxylic acid transport, was isolated and found unable to form effective bean nodules.The authors are with the Division of Biochemistry, Instituto de Investigaciones Biológicas Clemente Estable, Avda, Italia 3318, 11.600 Montevideo, Uruguay 相似文献
5.
A pot-culture experiment was carried out to investigate the effect of arbuscular mycorrhizal (AM) fungus (Glomus macrocarpum Tul. and Tul.) on plant growth and Cd2+uptake by Apium graveolens L. in soil with different levels of Cd2+. Mycorrhizal (M) and non-mycorrhizal (NM) plants were grown in soil with 0, 5, 10, 40 and 80 Cd2+ mg kg−1soil. The infectivity of the fungus was not affected by the presence of Cd2+ in the soil. M plants showed better growth and less Cd2+ toxicity symptoms. Cd2+ root : shoot ratio was higher in M plants than in NM plants. These differences were more evident at highest Cd2+ level (80 mg kg−1 soil). Chlorophyll a and chlorophyll b concentrations were significantly higher in AM-inoculated celery leaves. The dilution effect due to increased biomass, immobilization
of Cd2+ in root and enhanced P-uptake in M plants may be related to attenuation of Cd2+toxicity in celery. 相似文献
6.
Expression of the light-inducible (lipA) gene in Arthrobacter photogonimos is repressed by Ca2+ at a concentration greater than 0.1 M. Expression of lipA was induced by relatively high concentrations of Zn2+ Ni2+ or Co2+ in cell suspensions, an effect that was blocked by an increase in the concentration of Ca2+ in the medium. Zn2+ and other metals apparently overcame repression by Ca2+ by competing for a cellular binding site. Expression of lipA was also induced when the amount of free Ca2+ was lowered with ethylene-bis (oxyethylenenitrilo)tetraacetic acid (EGTA). Our results show that the lipA gene does not require Zn2+ or other divalent cation for expression and that it is regulated negatively by Ca2+.Accumulation of the mature product of this gene (light-inducible protein, LIP) was minimal in the presence of EGTA. Accumulation increased 10-to 20-fold when divalent cations such as Ca2+, Mn2+, Cu2+ or Zn2+ were added to cell suspensions treated with chelator. These divalent cations, which allowed the protein to achieve a protease-resistant form on the cell surface, could be substituted by protease inhibitors such as antipain, leupeptin or 1,10-phenanthroline. Our data can be explained by a biparous mechanism in which divalent cations regulate both expression of the lipA gene and accumulation of the gene product.Abbreviations LIP
light-inducible protein
- BAPTA
1,2-bis(o-aminophenoxy)ethanc-N,N,N,N-tetraacetic acid 相似文献
7.
Dipicolinic acid synthesis inPenicillium citreoviride strain 3114 was inhibited by Ca2+ ions, but not by Ba2+, Cu2+or Fe2+. Among the metals tested, only Zn2+ inhibited the synthesis of dipicolinic acid and promoted sporulation. None of these metals reversed the inhibition by Ca2+ or Zn2+. A mutant 27133-dpa-ca selected for resistance to feedback inhibition by dipicolinic acid: Ca2+ complex showed cross-resistance to inhibition by dipicolinic acid: Zn2+. Both 3114 and271 33-dpa-ca excreted a number of aliphatic and amino acids during secondary metabolism of dipicolinic acid. In the presence of 1000 ppm
of Ca2+, accumulation of citric acid and α-aminoadipic acid was completely inhibited under conditions of inhibition of dipicolinic
acid in parent strain 3114 but not in the mutant. Citric acid with or without Ca2+ did not inhibit thede novo synthesis of dipicolinic acid in the strain 3114. In fact, citric acid in the presence of Ca2+ improved significantly rate of dipicolinic acid synthesis. Apart from resistance to feed back inhibition by dipicolinic acid:
Ca2+ complex, mutant differed from the parent in three other aspectsviz. (i) dipicolinic acid synthesis was not subject to catabolite repression by glucose, (ii) sporulation as well as dipicolinic
acid synthesis was dependent on the presence of Ca2+ ions in the medium and (iii) Mg2+ requirement for the mutant increased three fold. Higher requirement of the Mg2+ could be partially relieved by Ca2+ during secondary metabolism. The results support the inference thatde novo synthesis of dipicolinic acid is regulated through feedback inhibition by dipicolinic acid: Ca2+complex. 相似文献
8.
The spatial distribution of cations was assayed qualitatively and quantitatively in tentacular nematocytes of Hydra vulgaris in a scanning transmission electron microscope by means of x-ray microanalysis performed on 100 nm thick freeze-dried cryosections. The matrix of undischarged cysts (stenoteles, desmonemes and isorhizas) was found to contain mainly K+. In isolated nematocysts of Hydra the intracapsular potassium can be readily substituted by practically any other mono- and divalent cation (Na+, NH4
+, Mn2+, Co2+, Mg2+, Ca2+, Fe2+) all, except Fe2+, without impairing the ability of the cyst to respond to the chemical triggering with dithioerythritol or proteases. Monovalent cations increase the osmotically generated intracapsular pressure compared to divalent ions. 相似文献
9.
Masa-aki Okuyama Yoshihiro Kobayashi Masahiro Inouhe Hiroshi Tohoyama Masanori Joho 《Biometals》1999,12(4):307-314
Copper-induced metallothionein (MT) synthesis in Saccharomyces cerevisiae was investigated in order to associate this exclusively with Cu2+
in vivo, when cultured in nutrient medium containing other heavy metal ions. Expression of the CUP1 promoter/lacZ fusion gene was inhibited by all heavy metal ions tested, especially Cd2+ and Mn2+. By adding Cd2+ and Mn2+ at 10 M concentration, the -galactosidase activity decreased by about 80% and 50% of the maximum induction observed with 1 mM CuSO4, respectively. Furthermore, cell growth was markedly inhibited by combinations of 1 mM-Cu2+ and 1 M-Cd2+. Therefore, the yeast S. cerevisiae could not rely on MT synthesis as one of the copper-resistance mechanisms, when grown in a Cd2+ environment. In contrast, the presence of Mn2+ in the nutrient medium showed alleviation rather than growth inhibition by high concentrations of Cu2+. The recovery from growth inhibition by Mn2+ was due to decreased Cu2+ accumulation. Inhibitory concentrations of Co2+, Ni2+ and Zn2+ on expression of the CUP1p/lacZ fusion gene were at least one order of magnitude higher than that of Cd2+ and Mn2+. These results are discussed in relation to Cu2+ transport and Cu-induced MT synthesis in the copper-resistance mechanism of the yeast S. cerevisiae. 相似文献
10.
重金属铜、锌、镉复合胁迫对麻疯树幼苗生理生化的影响 总被引:2,自引:0,他引:2
该研究以Cu~(2+)、Zn~(2+)、Cd~(2+)单一胁迫为对照,探讨不同浓度的Cu~(2+)、Zn~(2+)、Cd~(2+)复合胁迫对麻疯树幼苗生理生化指标的影响。结果表明:随着Cu~(2+)、Zn~(2+)、Cd~(2+)浓度的增加,麻疯树幼苗叶片中的蛋白质(Pro)、丙二醛(MDA)含量均逐渐增加,其叶片叶绿素含量随着Zn~(2+)胁迫浓度的增加呈现出先降后升的趋势,在中等浓度(100 mg·L-1)的Zn~(2+)胁迫时含量最低、随着Cu~(2+)胁迫浓度的增加叶绿素含量先升高后降低,在Cu~(2+)浓度为200 mg·L-1时含量最高,达到1 200 mg·g-1FW; Cd~(2+)胁迫对叶绿素含量和根系活力无明显影响。根系活力在Zn~(2+)浓度为100 mg·L~(-1)时最强,随着Cu~(2+)浓度的增加而减弱。低浓度的Cu~(2+)、Zn~(2+)、Cd~(2+)对过氧化物酶活性和可溶性糖含量都具有促进作用。Cu~(2+)、Zn~(2+)、Cd~(2+)复合胁迫时对可溶性蛋白、叶绿素和丙二醛含量均无明显影响,随着复合胁迫时浓度的增加,可溶性糖含量和根系活力先增后减。这表明麻疯树对三种重金属的胁迫具有一定的抗性,过高浓度的胁迫会影响麻疯树幼苗生理生化的一些指标,但是麻疯树可以通过自身的防御系统使伤害降到最小。此外,重金属复合胁迫可以在一定程度上减轻单一胁迫对麻疯树幼苗造成的毒害作用。 相似文献
11.
Effects of Metal Ions on the Conformation and Activity of Acutolysin D from Agkistrodon Acutus Venom
Acutolysin D, isolated from the venom of Agkistrodon acutus, possesses marked haemorrhagic and proteolytic activities. The molecular weight and the absorption coefficients (A
1%
280) of acutolyisn D have been determined to be 47,850 ± 8 amu and 9.3 by mass spectrometer and UV spectrum, respectively. The effects of metal ions on the conformation and activity of acutolysin D have been studied by following fluorescence, circular dichroism and biological activity measurements. Acutolysin D contains two Ca2+-binding sites and two Zn2+-binding sites determined by atomic absorption spectrophotometer. Zn2+ is essential for the enzyme activities of acutolysin D, however, the presence of 1 mM Zn2+ significantly decreases its caseinolytic activity and intrinsic fluorescence intensity at pH 9.0 due to Zn(OH)2 precipitate formation. Ca2+ is important for the structural integrity of acutolysin D, and the presence of 1 mM Ca2+ markedly enhances its caseinolytic activity. Interestingly, the caseinolytic activity which is inhibited partly by Cu2+, Co2+, Mn2+ or Tb3+ and inhibited completely by Cd2+, is enhanced by Mg2+. The fluorescence intensity of the protein decreases in the presence of Cu2+, Co2+, Cd2+ or Mn2+, but neither for Ca2+, Mg2+ nor for Tb3+. Zn2+, Ca2+, Mg2+, Cu2+, Mn2+, Co2+ and Tb3+ have slight effects on its secondary structure contents. In addition, Cd2+ causes a marked increase of antiparallel β-sheet content from 45.5% to 60.2%. 相似文献
12.
Qingxin Zhao Sheng Yuan Yuling Zhang Hong Zhu Chuanchao Dai Fang Yang Fengmin Han 《World journal of microbiology & biotechnology》2007,23(8):1057-1064
Pectate lyase A (PelA) of Aspergillus nidulans was successfully expressed in Escherichia coli and effectively purified using a Ni2+-nitrilotriacetate-agarose column. Enzyme activity of the recombinant PelA could reach 360 U ml−1 medium. The expressed PelA exhibited its optimum level of activity over the range of pH 7.5–10 at 50°C. Mn2+, Ca2+, Fe2+, Mg2+ and Fe3+ ions stimulated the pectate lyase activity, but Cu2+ and Zn2+ inhibited it. The recombinant PelA had a V
max of 77 μmol min−1 mg−1 and an apparent K
m of 0.50 mg ml−1 for polygalacturonic acid. Low-esterified pectin was the optimum substrate for the PelA, whereas higher-esterified pectin
was hardly cleaved by it. PelA efficiently macerated mung bean hypocotyls and potato tuber tissues into single cells. 相似文献
13.
M. López-Serrano M. A. Ferrer M. A. Pedreño A. Ros Barceló 《Plant Cell, Tissue and Organ Culture》1997,47(3):207-212
Grapevine (Vitis vinifera cv. Monastrell) cell suspension cultures were treated with 1.5 mM fosetyl-Al, a frequently used systemic fungicide for grapevine
diseases caused by oomycetes. These cells showed a reduction in the level of peroxidase activity secreted into the culture
media when compared to non-treated cells, the effect being mainly related to a decrease in the level of the basic B1 peroxidase isozyme. The effect of fosetyl-Al on peroxidase was analogous to that observed with the Ca2+-channel blockers Co2+, Cd2+ and La3+, and was counteracted by Ca2+ ions, but was not reversed when the Ca2+-ionophore A23187 was added to the culture media. Moreover, the effect of fosetyl-Al on peroxidase activity and peroxidase
isozymes was also partially reversed by Mg2+ ions but not by Sr2+, and was accentuated by Ba2+ ions. These results suggested that Ca2+ and Mg2+ ions specifically overcome the inhibitory effect of fosetyl-Al on peroxidase. In this context, an apoplastic Ca2+/Mg2+-displacement hypothesis is proposed for the mechanism of action of fosetyl-Al on peroxidase from grapevine cells. 相似文献
14.
The phospholipid requirement of the (Ca2+ + Mg2+)-ATPase present in a membrane fraction from human platelets was studied using various purified phospholipases. Only those phospholipases, which hydrolyse the negatively charged phospholipids, inhibited the (Ca2+ + Mg2+)-ATPase activity. The ATPase activity could be restored by adding mixed micelles of Triton X-100 and phosphatidylserine or phosphatidylinositol. Micelles with phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine or sphingomyelin could not be used for reconstitution and inhibited the activity of the native enzyme. 相似文献
15.
Excretion of pyruvate in nickel toxicity in wild type and Ni2+ resistant mutants ofNeurospora crassa
The parent wild strainNeurospora crassa Em 5297a and three Ni2+ resistantNeurospora crassa mutants have been shown to excrete pyruvate into the culture medium in Ni2+ and Co2+ toxicities. Ni2+ has a more pronounced effect in this regard. The excretion is progressive with growth inhibition and is abolished by Mg2+ in all strains and by Fe3+ partially in the Em strain but not inNeurospora crassa NiR1. Pyruvate, citrate and malate supplementation reverse growth inhibition caused by excess Ni2+, but with concomitant suppression of Ni2+ accumulation. It is suggested that one of the features of Ni2+ toxicity inNeurospora crassa is a derangement in carbohydrate metabolism at step(s) beyond pyruvate and that this is possibly due to decreased invivo activity of Mg2+ dependent processes 相似文献
16.
Mattias D. Hansson Mats Lindstam Mats Hansson 《Journal of biological inorganic chemistry》2006,11(3):325-333
Ferrochelatase (EC 4.99.1.1), the terminal enzyme in the heme biosynthetic pathway, catalyzes the insertion of Fe2+ into protoporphyrin IX, generating heme. In vitro assays have shown that all characterized ferrochelatases can also incorporate
Zn2+ into protoporphyrin IX. Previously Zn2+ has been observed at an inner metal binding site close to the porphyrin binding site. Mg2+, which stimulates Zn2+ insertion by Bacillus subtilis ferrochelatase, has been observed at an outer metal binding site. Exchange of Glu272 to a serine eliminated the stimulative
effect of Mg2+. We found that Zn2+ quenched the fluorescence of B. subtilis ferrochelatase and this quenching was used to estimate the metal affinity. Trp230 was identified as the intrinsic fluorophore
responsible for the observed quenching pattern. The affinity for Zn2+ could be increased by incubating the ferrochelatase with the transition state analogue N-methyl mesoporphyrin IX, which reflected a close collaborative arrangement between the two substrates in the active site.
We also showed that the affinity for Zn2+ was lowered in the presence of Mg2+ and that bound Zn2+ was released upon binding of Mg2+. In the ferrochelatase with a Glu272Ser modification, the interaction between Zn2+ and Mg2+ was abolished. It could thereby be demonstrated that the presence of a metal at one metal binding site affected the metal
affinity of another, providing the enzyme with a site that regulates the enzymatic activity. 相似文献
17.
The growth capability of Trichoderma harzianum Rifaii Tl was tested on Malt Extract and Czapeks Dox agar containing different concentrations of Cu2+, Zn2+, Mn2+, Fe2+ and Ca2+. The T. harzianum Tl isolate was observed to produce mycelia and spores in various mineral-containing media. It showed the lowest tolerance
to Ca2+ and the highest tolerance to Fe2+. Solubilization capability of T. harzianum Tl for some insoluble minerals via acidification of medium has been tested on MnO2, CuO, Fe2O3 and metallic Zn. T. harzianum Tl was able to solubilize MnO2 and metallic Zn in a liquid medium. 相似文献
18.
Extracellular chitinase from Alcaligenes xylosoxydans was purified to electrophoretic homogeneity using affinity and gel filtration chromatography. The molecularmass of chitinase was estimated to be 45 kDa and44 kDa by SDS-PAGE and gel-filtration, respectively. The enzyme was optimally active at 50 °C (over 30 min) and pH 5. Activity staining after PAGE showed a single band. The Km for chitin was 3 g l–1. Cu2+ and Na+ at 5 mM inhibited chitinase activity to 25% while Ca2+, Mg2+ and Ba2+ had no effect at the same concentration. The purified enzyme degraded mycelia of Aspergillus niger. 相似文献
19.
以拟南芥野生型和类受体蛋白激酶基因CRK45的T-DNA插入突变体crk45为材料,采用差异基因表达筛选技术检测ABA处理后野生型和crk45中基因表达的差异。结果显示:(1)crk45突变体中有1个基因的表达比野生型高约4倍。(2)NCBI数据库检索表明,该基因编码的蛋白具有EF手型结构,蛋白序列全长为130个氨基酸,是典型的Ca2+结合蛋白,故命名为CRK45抑制的钙离子结合蛋白(CICBP)。(3)Northern blotting分析结果显示,ABA处理后crk45突变体中CICBP的表达明显升高,证明CICBP基因的确受ABA诱导,且其表达受CRK45的抑制。(4)外源75mmol/L的Ca2+处理后,crk45突变体的萌发率(30.8%)显著高于野生型(17.16%),说明在Ca2+介导下CRK45的功能是抑制种子萌发。(5)qRT-PCR检测显示,野生型中CRK45的表达受Ca2+诱导明显升高,而crk45突变体中的表达一直保持很低,说明crk45突变体是一个基因敲除突变体;Ca2+处理后crk45突变体中CICBP基因表达上调,而野生型中CICBP的表达反而降低,说明Ca2+处理下CRK45抑制CICBP基因的表达。研究表明,ABA或Ca2+处理后,CRK45通过负调控CICBP基因的表达,从而抑制拟南芥种子萌发。 相似文献
20.
河流、湖泊等水生环境中普遍存在的重金属污染破坏水生生态系统并间接威胁人类健康。为探究重金属胁迫下水生昆虫花翅摇蚊(Chironomus kiiensis)生态毒理,测定了重金属Cd2+和Pb2+胁迫对花翅摇蚊化蛹率和羽化率的影响,检测了摇蚊的口器致畸与富集效应。研究结果表明,Cd2+和Pb2+影响摇蚊幼虫化蛹和羽化过程,单一重金属离子处理14 d Pb2+处理组的化蛹率和羽化率分别为22.22%和8.89%,低于Cd2+的化蛹率(25.56%)和羽化率(11.11%),表现出更强的抑制效应。混合离子1:2和2:1配比处理组化蛹率和羽化率均为11.11%和4.44%,显著低于单一重金属离子胁迫下的化蛹率和羽化率。单一重金属离子及混合离子处理均能导致花翅摇蚊幼虫口器致畸,表现为上颚前齿断裂,中齿和基齿磨损、缺失,下唇板齿部不规则,下唇板边缘齿与中央齿磨损、断裂、增生、缺失。不同重金属离子处理下幼虫口器致畸率不同,并与暴露时间呈正相关,其中1:2配比处理14 d致畸率达到40.61%。重金属离子在摇蚊幼虫体内产生生物富集效应,单一重金属离子处理下的Pb2+富集含量7 d至14 d由11.46 mg/kg上升至31.32 mg/kg,不同配比混合离子处理下Pb2+富集含量均呈增加趋势,其中1:2配比处理组由15.48 mg/kg上升至42.50 mg/kg,而Cd2+在单一重金属与1:1混合离子处理组7 d至14 d的富集含量无显著性变化,2:1配比处理组由14.20 mg/kg下降至9.52 mg/kg,1:2配比由5.85 mg/kg上升至20.99 mg/kg。这些研究结果表明Cd2+和Pb2+胁迫影响花翅摇蚊幼虫生长发育且口器出现畸型,与重金属在幼虫体内的富集密切相关,为研究重金属对水生生态系统多重效应提供了理论依据。 相似文献