Evaluation of Histidine Reactivity and Byproduct Formation during Peptide Chlorination
Evaluation of Histidine Reactivity and Byproduct Formation during Peptide Chlorination
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DOI：
10.1021/acs.est.0c07408
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发表时间：
2021-01-25
影响因子：
11.4
通讯作者：
Mitch, William A.
中科院分区：
文献类型：
--
作者：
Choe, Jong Kwon;Hua, Lap-Cuong;Mitch, William A.
氯与肽结合氨基酸反应产生的共价修饰有助于病原体灭活和消毒副产物（DBP）的形成。先前的研究表明，组氨酸是7种氯反应性氨基酸中活性第三强的氨基酸，可形成2-氯组氨酸、2-氧组氨酸或低分子量的副产物，如三卤甲烷。本研究表明，组氨酸对氯转化产物（转化时间尺度为小时至天）的反应性低于7种氯反应性氨基酸中的5种，包括酪氨酸（转化时间尺度为分钟）。氯优先针对酪氨酸而不是组氨酸，这表明氯与酪氨酸和其他活性更强的氨基酸的反应在短时间内对蛋白质的结构修饰有更大的作用，与病原体失活有关。在与处理厂或分配系统中消毒副产物形成相关的较长时间尺度上，本研究确定-氰丙氨酸是氯与肽结合组氨酸反应的主要转化产物，1天后摩尔产率接近50%。虽然氯化组氨酸中间体的产率较低（最高约为5%），但常规低分子量dbp（如三卤甲烷）的累积浓度为
The covalent modifications resulting from chlorine reactions with peptide-bound amino acids contribute to pathogen inactivation and disinfection byproduct (DBP) formation. Previous research suggested that histidine is the third most reactive of the seven chlorine-reactive amino acids, leading to the formation of 2-chlorohistidine, 2-oxohistidine, or low-molecular-weight byproducts such as trihalomethanes. This study demonstrates that histidine is less reactive toward formation of chlorine transformation products (transformation time scale of hours to days) than five of the seven chlorine-reactive amino acids, including tyrosine (transformation time scale of minutes). Chlorine targeted tyrosine in preference to histidine within peptides, indicating that chlorine reactions with tyrosine and other more reactive amino acids could contribute more to the structural modifications to proteins over the short time scales relevant to pathogen inactivation. Over the longer time scales relevant to disinfection byproduct formation in treatment plants or distribution systems, this study identified beta-cyanoalanine as the dominant transformation product of chlorine reactions with peptide-bound histidine, with molar yields of similar to 50% after 1 day. While a chlorinated histidine intermediate was observed at lower yields (maximum similar to 5%), the cumulative concentration of the conventional low-molecular-weight DBPs (e.g., trihalomethanes) was