丙烯酰胺存在于热加工食品中,它具有毒性和致癌性。L-天冬酰胺酶能有效调控丙烯酰胺的生成。然而,目前的L-天冬酰胺酶有缺点,如热稳定性差,低催化活性,和较差的底物特异性,从而限制了它们在食品工业中的效用。为了解决这个问题,这项研究采用共识设计来预测影响谷氨酸棒杆菌L-天冬酰胺酶(CgASNase)热稳定性的关键残基。随后,应用了位点饱和突变和组合突变技术的组合,以产生双突变酶L42T/S213N.值得注意的是,L42T/S213N显示出显著增强的热稳定性,而对其酶活性没有实质性影响。值得注意的是,它在40°C时的半衰期达到了令人印象深刻的13.29±0.91分钟,超过CgASNase(3.24±0.23分钟)。此外,L42T/S213N增强的热稳定性可以归因于增加的正表面电荷和更对称的正电势,三维结构模拟和结构比较分析揭示了这一点。为了评估L42T/S213N对饼干中丙烯酰胺去除的影响,通过单因素试验和正交试验相结合,确定了丙烯酰胺去除的最佳处理条件,酶剂量为300IU/kg面粉,酶反应温度为40℃,酶反应时间为30分钟。在这些条件下,与对照组相比(464.74±6.68µg/kg),双突变酶处理饼干中的丙烯酰胺减少了85.31%,而野生型处理的饼干减少了68.78%。这些结果表明L42T/S213N是L-天冬酰胺酶工业应用的有希望的候选物。
Acrylamide is present in thermally processed foods, and it possesses toxic and carcinogenic properties. L-asparaginases could effectively regulate the formation of acrylamide at the source. However, current L-asparaginases have drawbacks such as poor thermal stability, low catalytic activity, and poor substrate specificity, thereby restricting their utility in the food industry. To address this issue, this study employed consensus design to predict the crucial residues influencing the thermal stability of Corynebacterium glutamicum L-asparaginase (CgASNase). Subsequently, a combination of site-point saturating mutation and combinatorial mutation techniques was applied to generate the double-mutant enzyme L42T/S213N. Remarkably, L42T/S213N displayed significantly enhanced thermal stability without a substantial impact on its enzymatic activity. Notably, its half-life at 40 °C reached an impressive 13.29 ± 0.91 min, surpassing that of CgASNase (3.24 ± 0.23 min). Moreover, the enhanced thermal stability of L42T/S213N can be attributed to an increased positive surface charge and a more symmetrical positive potential, as revealed by three-dimensional structural simulations and structure comparison analyses. To assess the impact of L42T/S213N on acrylamide removal in biscuits, the optimal treatment conditions for acrylamide removal were determined through a combination of one-way and orthogonal tests, with an enzyme dosage of 300 IU/kg flour, an enzyme reaction temperature of 40 °C, and an enzyme reaction time of 30 min. Under these conditions, compared to the control (464.74 ± 6.68 µg/kg), the acrylamide reduction in double-mutant-enzyme-treated biscuits was 85.31%, while the reduction in wild-type-treated biscuits was 68.78%. These results suggest that L42T/S213N is a promising candidate for industrial applications of L-asparaginase.