BACKGROUND Today, ultrasound is increasingly utilized in enzyme modification. Strongly dependent on the specific operational conditions, the modification effect brought by ultrasound can be activation and inactivation of enzymes. This work aims to study the ultrasound mechanisms under different conditions, to investigate the respective roles of free radical effect and mechanical effect in pectinase activation and inactivation, and to reveal the influence of pectinase concentration on the ultrasound-modification effect. RESULTS When ultrasound was introduced to a liquid system, generation of free radicals was positively correlated with ultrasound intensity and treatment duration, but negatively correlated with temperature. Thiourea with a concentration of 4 mM was selected as a free radical scavenger to effectively shield ultrasound free radicals. The highest enzyme activity of pectinase solutions at 0.1, 1.0, and 10.0 mg mL-1 was obtained at the same ultrasound intensity of 4.50 W mL-1 and time of 15 min, where the enzyme activity was increased by 68.24%, 20.98% and 18.83%, respectively. Furthermore, the addition of thiourea enhanced the enzyme activity at each tested ultrasound intensity and time, especially those exceeding the best conditions; it also eliminated the redshift phenomenon that was previously presented in the fluorescence spectra of pectinase samples. CONCLUSION Pectinase concentrations did not change the optimum ultrasound conditions for enzyme modification, but pectinase with a low concentration was more vulnerable to ultrasound treatment. During modification, ultrasound mechanical effects dominated in pectinase activation, while free radical effects dominated in the inactivation process. This article is protected by copyright. All rights reserved.

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用于果胶酶修饰的超声：潜在机制的研究

背景今天，超声越来越多地用于酶修饰。强烈依赖于具体的操作条件，超声波带来的修饰效果可以是酶的激活和失活。本工作旨在研究不同条件下的超声机制，研究自由基效应和机械效应在果胶酶活化和失活中的各自作用，揭示果胶酶浓度对超声改性效果的影响。结果当超声被引入液体系统时，自由基的产生与超声强度和治疗持续时间呈正相关，但与温度呈负相关。选择浓度为 4 mM 的硫脲作为自由基清除剂，以有效屏蔽超声自由基。在相同超声强度4.50 W mL-1和15 min时间下，0.1、1.0和10.0 mg mL-1果胶酶溶液的酶活性最高，酶活性分别提高了68.24%、20.98%和20.98%。分别为 18.83%。此外，硫脲的加入增强了每个测试超声强度和时间的酶活性，尤其是那些超过最佳条件的；它还消除了先前出现在果胶酶样品荧光光谱中的红移现象。结论果胶酶浓度不改变酶修饰的最佳超声条件，但低浓度果胶酶更易受到超声处理。在修饰过程中，超声机械效应在果胶酶激活中占主导地位，而自由基效应在灭活过程中占主导地位。本文受版权保护。版权所有。