共查询到18条相似文献,搜索用时 125 毫秒
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由高盐环境中生长的微生物里分离出的嗜盐酶在高盐度下仍然具有催化活性,工业上具有良好的应用前景。一些嗜盐酶已被克隆纯化出来,它们的分子结构特点也已经被广泛研究。该文从嗜盐酶的蛋白质序列和结构特征等方面综述了嗜盐酶嗜盐的分子结构基础研究进展,分析了存在的问题并对未来工作提出了展望。研究嗜盐酶盐适应性的分子基础,可以为新的功能蛋白的发展和鉴定提供依据。 相似文献
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中度嗜盐菌的研究进展 总被引:37,自引:7,他引:37
地球上存在着多种多样的盐域环境,这类环境中有自然形成的,如死海,美国的大盐湖等水环境,还有盐土环境;人工形成的如盐场、盐池等;另外,还有很多盐腌制的食品。自然界的高盐环境由于形成过程和所处地质情况的不同其离子组成和盐浓度有很大差异。生活在这些高盐环境中的动、植物物种较为有限,而以处于不同类群的微生物,如绿藻、嗜盐古菌及嗜盐和耐盐的细菌等为主要生命形式。根据微生物对盐浓度的反应可分为不同的种(如表1[1])。 相似文献
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嗜盐古菌是一类生活于极端高盐环境的化能异养型原核微生物,其所分泌的胞外酶(外泌酶)具有在高盐条件下仍能保持活性的特点,在制革工业、高盐有机废水处理和泡菜加工等腌制食品方面发挥重要用途。本文对嗜盐古菌的胞外蛋白酶、淀粉酶、酯酶等几种常见胞外酶的来源和基本酶学性质的最新研究进展进行综述,为更好地开发利用嗜盐古菌胞外酶资源提供参考。 相似文献
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高盐废水因具有硬度高、可生化性差、水质成分复杂等特点,是较难处理的工业废水之一。现有物化处理技术存在运行成本高、处理效率低、二次污染重等诸多瓶颈。耐盐/嗜盐微生物可在高盐环境下进行正常生理代谢,因此,开发经济、高效、可靠的高盐废水生物处理技术有望成为高盐废水处理的主流方向之一。本文系统综述了耐盐/嗜盐微生物盐溶、胞内小分子相容溶质积累、蛋白质稳定和细胞表面稳定等高渗透压适应策略。由于嗜盐微生物存在生长条件苛刻、功能微生物种类稀缺等问题,因此,耐盐微生物在高盐废水处理的未来应用空间更大。最新研究发现强化调控技术(电、光、磁)可提升微生物的高渗透压适应能力,其中电调控技术或是未来高盐废水生物处理的重点研究方向。 相似文献
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极端嗜盐古生菌(Natrinema sp.)R6-5胞外嗜盐蛋白酶的纯化和性质研究 总被引:1,自引:0,他引:1
采用bacitracin-Sepharose 4B亲和层析的方法得到凝胶电泳均一的来自极端嗜盐古生菌(Natrinema sp.)R6-5的胞外嗜盐蛋白酶。经SDS-PAGE分析该酶亚基分子量为62kDa。PMSF对它的活性完全抑制,表明它是一种丝氨酸蛋白酶,该酶反应的最适NaCl浓度为3mol/L,最适温度为45℃,最适pH值为8.0。在高盐条件下能维持高活性并十分稳定,具有重要的潜在应用价值。 相似文献
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An extracellular protease has been purified from the extreme halophile, Halobacterium halobium. The irreversible inactivation kinetics of this halophilic protease in salt concentrations below 4M consists of autolytic and nonautolytic (steady-state denaturation) components. Addition of organic solvents has a dramatic effect on enzyme stability in low salt media. For example, in 0.36M NaCl, the inactivation rate constant for the nonautolytic component in 20% (v/v) ethylene glycol is ca. 3 orders of magnitude lower than in 20% (v/v) tetrahydrofuran. Enzyme stability in different aqueous/organic solvent mixtures correlates strongly to the salting-out capacity of the solvent. Solvents that act to increase the apparent hydrophobicity of the enzyme's core stabilize the enzyme in much the same way as salting-out salts. This mechanism is not important for the nonhalophilic protease, subtilisin Carlsberg, and demonstrates that halophilic enzymes have evolved highly specialized reaction medium requirements. Moreover, through the use of organic solvents, it is shown that high concentrations of salts are not absolutely necessary for high enzyme stability, and this may have important process considerations. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 471-479, 1997. 相似文献
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Samuel Blanquart Mathieu Groussin Aline Le Roy Gergely J Szllosi Eric Girard Bruno Franzetti Manolo Gouy Dominique Madern 《Molecular biology and evolution》2021,38(9):3754
Extreme halophilic Archaea thrive in high salt, where, through proteomic adaptation, they cope with the strong osmolarity and extreme ionic conditions of their environment. In spite of wide fundamental interest, however, studies providing insights into this adaptation are scarce, because of practical difficulties inherent to the purification and characterization of halophilic enzymes. In this work, we describe the evolutionary history of malate dehydrogenases (MalDH) within Halobacteria (a class of the Euryarchaeota phylum). We resurrected nine ancestors along the inferred halobacterial MalDH phylogeny, including the Last Common Ancestral MalDH of Halobacteria (LCAHa) and compared their biochemical properties with those of five modern halobacterial MalDHs. We monitored the stability of these various MalDHs, their oligomeric states and enzymatic properties, as a function of concentration for different salts in the solvent. We found that a variety of evolutionary processes, such as amino acid replacement, gene duplication, loss of MalDH gene and replacement owing to horizontal transfer resulted in significant differences in solubility, stability and catalytic properties between these enzymes in the three Halobacteriales, Haloferacales, and Natrialbales orders since the LCAHa MalDH. We also showed how a stability trade-off might favor the emergence of new properties during adaptation to diverse environmental conditions. Altogether, our results suggest a new view of halophilic protein adaptation in Archaea. 相似文献
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Allers T 《Bioengineered bugs》2010,1(4):288-290
Halophilic enzymes function optimally at high salt concentrations and are active at low water availability. Such conditions are encountered at elevated concentrations of solutes such as salts and sugars, and at high concentrations of organic solvents. However, expression in heterologous hosts such as Escherichia coli can cause problems, since halophilic proteins typically misfold and aggregate in conditions of low ionic strength. We have harnessed the sophisticated genetic tools available for the haloarchaeon Haloferax volcanii, to develop a system for the overexpression and purification of halophilic proteins under native conditions. 相似文献
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Halophilic enzymes have been established for their stability and catalytic abilities under harsh operational conditions. These have been documented to withstand denaturation at high temperature, pH, organic solvents, and chaotropic agents. However, this stability is modulated by salt. The present study targets an important aspect in understanding protein–urea/GdmCl interactions using proteases from halophilic Bacillus sp. EMB9 and non-halophilic subtilisin (Carlsberg) from Bacillus licheniformis as model systems. While, halophilic protease containing 1 % (w/v) NaCl (0.17 M) retained full activity towards urea (8 M), non-halophilic protease lost about 90 % activity under similar conditions. The secondary and tertiary structure were lost in non-halophilic but preserved for halophilic protein. This effect could be due to the possible charge screening and shielding of the protein surface by Ca2+ and Na+ ions rendering it stable against denaturation. The dialyzed halophilic protease almost behaved like the non-halophilic counterpart. Incorporation of NaCl (up to 5 %, w/v or 0.85 M) in dialyzed EMB9 protease containing urea/GdmCl, not only helped regain of proteolytic activity but also evaded denaturing action. Deciphering the basis of this salt modulated stability amidst a denaturing milieu will provide guidelines and templates for engineering stable proteins/enzymes for biotechnological applications. 相似文献
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Yonezawa Y Tokunaga H Ishibashi M Taura S Tokunaga M 《Protein expression and purification》2003,27(1):128-133
Most typical halophilic enzymes from extremely halophilic archaea require high concentrations of salt for their activity and stability. These enzymes are inactive in Escherichia coli unless refolded in the presence of salts in vitro. In this report, we describe cloning of the ndk gene of nucleoside diphosphate kinase from a moderately halophilic eubacterium and overexpression of the protein in E. coli as an N-terminal hexa-His fusion to facilitate its purification on Ni-NTA affinity resin. We demonstrate evidence that the protein is properly folded and exhibits the same specific activity and stability as the native protein from Halomonas cells. 相似文献
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Enzymes produced by halophilic archaea are generally heat resistant and organic solvent tolerant, and accordingly important for biocatalytic applications in ‘green chemistry’, frequently requiring a low-water environment. NAD+-dependent glutamate dehydrogenase from an extremely halophilic archaeon Halobacterium salinarum strain NRC-36014 was selected to explore the biotechnological potential of this enzyme and genetically engineered derivatives. Over-expression in a halophilic host Haloferax volcanii provided a soluble, active recombinant enzyme, not achievable in mesophilic Escherichia coli, and an efficient purification procedure was developed. pH and salt dependence, thermostability, organic solvent stability and kinetic parameters were explored. The enzyme is active up to 90 °C and fully stable up to 70 °C. It shows good tolerance of various miscible organic solvents. High concentrations of salt may be substituted with 30 % DMSO or betaine with good stability and activity. The robustness of this enzyme under a wide range of conditions offers a promising scaffold for protein engineering. 相似文献