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Deep Eutectic Solvents as New Reaction Media to Produce Alkyl-Glycosides Using Alpha-Amylase from Thermotoga maritima

机译:深度共晶溶剂作为新的反应介质,使用Thermotoga Maritima使用α-淀粉酶生产烷基糖苷

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摘要

Deep Eutectic Solvents (DES) were investigated as new reaction media for the synthesis of alkyl glycosides catalyzed by the thermostable α-amylase from Thermotoga maritima Amy A. The enzyme was almost completely deactivated when assayed in a series of pure DES, but as cosolvents, DES containing alcohols, sugars, and amides as hydrogen-bond donors (HBD) performed best. A choline chloride:urea based DES was further characterized for the alcoholysis reaction using methanol as a nucleophile. As a cosolvent, this DES increased the hydrolytic and alcoholytic activity of the enzyme at low methanol concentrations, even when both activities drastically dropped when methanol concentration was increased. To explain this phenomenon, variable-temperature, circular dichroism characterization of the protein was conducted, finding that above 60 °C, Amy A underwent large conformational changes not observed in aqueous medium. Thus, 60 °C was set as the temperature limit to carry out alcoholysis reactions. Higher DES contents at this temperature had a detrimental but differential effect on hydrolysis and alcoholysis reactions, thus increasing the alcoholyisis/hydrolysis ratio. To the best of our knowledge, this is the first report on the effect of DES and temperature on an enzyme in which structural studies made it possible to establish the temperature limit for a thermostable enzyme in DES.
机译:研究了深度共晶溶剂(DES)作为新的反应介质,用于合成来自Thermotoga Maritima Amy A的热稳定α-淀粉酶催化的烷基糖苷。当在一系列纯粹的DES中测定时,酶几乎完全失活,但作为富溶剂, DES含有醇,糖和酰胺作为氢键供体(HBD)表现最佳。氯化胆胆碱:基于尿素的DES,其特征在于使用甲醇作为亲核试剂的醇解反应。作为一种助溶剂,即使在甲醇浓度增加时,即使在甲醇浓度增加时,也增加了在低甲醇浓度下酶的水解和醇的活性。为了解释这种现象,进行蛋白质的可变温度,圆形二色性表征,发现在60℃以上,在水性介质中未观察到未观察到的大量大构象变化。因此,将60℃设定为进行醇解反应的温度极限。该温度的更高的DES含量对水解和醇解反应有害但差异效果,从而增加了醇酶/水解比。据我们所知,这是第一份关于DES和温度对酶影响的报告,其中结构研究使得可以在DES中确定热稳定酶的温度限制。

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