Jing Mingyang, Tang Rui, Han Guangye, Zhang Shansheng, Liu Rutao
School of Environmental Science and Engineering, Shandong University, America CRC for Environment & Health, 72# Jimo Binhai Road, Qingdao, Shandong 266237, P.R. China.
Penglai Jiaxin Dye Chemical Co., Ltd, 1#Jiaxin Road, Yantai, Shandong 265601, P.R. China.
Toxicol Res (Camb). 2020 May 7;9(3):182-190. doi: 10.1093/toxres/tfaa013. eCollection 2020 Jun.
Soil contamination with heavy metal could induce the alteration of soil ecological environments, and soil enzyme activities are sensitive indicators for the soil toxicology. Xylanase is one of predominant soil enzymes related to carbon nitrogen cycle. In this work, we explored the underlying mechanisms for conformational and enzymatic activity alterations of xylanase after silver and lead exposure at molecular level with systematical measurements including multiple spectroscopic methods, isothermal titration calorimetry, and enzymatic activity. Both silver and lead could loosen and unfold the skeleton of xylanase with the quenching of endogenous fluorescence. Silver interacted with xylanase forming larger-size aggregations through Van der Waals forces and hydrogen bonding, while lead interacted with xylanase forming larger-size aggregations through hydrophobic force. Silver and lead induced an obvious loss (67.1 and 56.31%) of the xylanase enzymatic activity, but silver has a greater impact on xylanase than that of lead. The xylanase enzymatic activity significantly decreased due to the conformational alterations. The negative effect of silver exposure on xylanase structure and function was more prominent than that of lead.
土壤重金属污染会导致土壤生态环境的改变，而土壤酶活性是土壤毒理学的敏感指标。木聚糖酶是与碳氮循环相关的主要土壤酶之一。在这项工作中，我们通过包括多种光谱方法、等温滴定量热法和酶活性在内的系统测量，在分子水平上探索了银和铅暴露后木聚糖酶构象和酶活性改变的潜在机制。银和铅都会使木聚糖酶的骨架松弛并展开，同时内源荧光猝灭。银通过范德华力和氢键与木聚糖酶相互作用形成更大尺寸的聚集体，而铅通过疏水作用与木聚糖酶相互作用形成更大尺寸的聚集体。银和铅导致木聚糖酶活性明显丧失（分别为67.1%和56.31%），但银对木聚糖酶的影响比铅更大。由于构象改变，木聚糖酶的酶活性显著降低。银暴露对木聚糖酶结构和功能的负面影响比铅更突出。
