Comparative studies of endonuclease I from cold-adapted Vibrio salmonicida and mesophilic Vibrio cholerae
Comparative studies of endonuclease I from cold-adapted Vibrio salmonicida and mesophilic Vibrio cholerae
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DOI：
10.1111/j.1742-4658.2006.05580.x
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发表时间：
2007-01-01
期刊：
影响因子：
5.4
通讯作者：
Moe, Elin
中科院分区：
文献类型：
--
作者：
Altermark, Bjorn;Niiranen, Laila;Moe, Elin
核酸内切酶I是存在于许多不同变形菌中的周质或胞外酶。编码来自嗜冷和轻度嗜盐细菌杀鲑弧菌和来自嗜温微咸水细菌霍乱弧菌的核酸内切酶I的endA基因已被克隆，在大肠杆菌中过表达，并纯化。的酶的性质的比较表明，在NaCl的要求，最佳pH值，温度稳定性和催化效率的两种蛋白质的大的差异。杀鲑弧菌EndA与霍乱弧菌EndA相比，具有较低的解折叠温度、较低的最适温度和较高的比活等典型的冷适应特性。热力学活化参数证实了杀鲑弧菌EndA的嗜冷性质，具有低得多的活化焓。酶活性的最佳条件与生物体生长的相应最佳要求完全一致，并且酶在生理浓度的NaCl下主要起DNA酶的作用。酶的周质或细胞外定位使它们不断暴露于细胞的外部环境，这可以解释这种生物化学性质的微调。
Endonuclease I is a periplasmic or extracellular enzyme present in many different Proteobacteria. The endA gene encoding endonuclease I from the psychrophilic and mildly halophilic bacterium Vibrio salmonicida and from the mesophilic brackish water bacterium Vibrio cholerae have been cloned, over-expressed in Escherichia coli, and purified. A comparison of the enzymatic properties shows large differences in NaCl requirements, optimum pH, temperature stability and catalytic efficiency of the two proteins. The V. salmonicida EndA shows typical cold-adapted features such as lower unfolding temperature, lower temperature optimum for activity, and higher specific activity than V. cholerae EndA. The thermodynamic activation parameters confirm the psychrophilic nature of V. salmonicida EndA with a much lower activation enthalpy. The optimal conditions for enzymatic activity coincide well with the corresponding optimal requirements for growth of the organisms, and the enzymes function predominantly as DNases at physiological concentrations of NaCl. The periplasmic or extracellular localization of the enzymes, which renders them constantly exposed to the outer environment of the cell, may explain this fine-tuning of biochemical properties.