Wang Ziquan, Tan Xiangping, Lu Guannan, Liu Yanju, Naidu Ravi, He Wenxiang
College of Natural Resources and Environment, Northwest A&F University, Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Yangling, 712100 Shaanxi, China.
Global Centre for Environmental Research, The Faculty of Science and Information Technology, University of Newcastle, University Drive, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), Mawson Lakes, SA 5095, Australia.
Ecotoxicol Environ Saf. 2018 Jan;147:266-274. doi: 10.1016/j.ecoenv.2017.08.050. Epub 2017 Sep 14.
Soil phosphatase, which plays an important role in phosphorus cycling, is strongly inhibited by Arsenic (As). However, the inhibition mechanism in kinetics is not adequately investigated. In this study, we investigated the kinetic characteristics of soil acid phosphatase (ACP) in 14 soils with varied properties, and also explored how kinetic properties of soil ACP changed with different spiked As concentrations. The results showed that the Michaelis constant (K) and maximum reaction velocity (V) values of soil ACP ranged from 1.18 to 3.77mM and 0.025-0.133mMh in uncontaminated soils. The kinetic parameters of soil ACP in different soils changed differently with As contamination. The K remained unchanged and V decreased with increase of As concentration in most acid and neutral soils, indicating a noncompetitive inhibition mechanism. However, in alkaline soils, the K increased linearly and V decreased with increase of As concentration, indicating a mixed inhibition mechanism that include competitive and noncompetitive. The competitive inhibition constant (K) and noncompetitive inhibition constant (K) varied among soils and ranged from 0.38 to 3.65mM and 0.84-7.43mM respectively. The inhibitory effect of As on soil ACP was mostly affected by soil organic matter and cation exchange capacity. Those factors influenced the combination of As with enzyme, which resulted in a difference of As toxicity to soil ACP. Catalytic efficiency (V/K) of soil ACP was a sensitive kinetic parameter to assess the ecological risks of soil As contamination.
土壤磷酸酶在磷循环中起着重要作用，但受到砷（As）的强烈抑制。然而，其动力学抑制机制尚未得到充分研究。在本研究中，我们调查了14种性质各异的土壤中酸性磷酸酶（ACP）的动力学特征，并探讨了土壤ACP的动力学性质如何随不同的砷添加浓度而变化。结果表明，在未受污染的土壤中，土壤ACP的米氏常数（K）和最大反应速度（V）值分别为1.18至3.77mM和0.025 - 0.133mM/h。不同土壤中土壤ACP的动力学参数随砷污染的变化情况不同。在大多数酸性和中性土壤中，随着砷浓度的增加，K保持不变而V降低，表明为非竞争性抑制机制。然而，在碱性土壤中，随着砷浓度的增加，K呈线性增加而V降低，表明为包括竞争性和非竞争性的混合抑制机制。竞争性抑制常数（K）和非竞争性抑制常数（K）因土壤而异，分别在0.38至3.65mM和0.84 - 7.43mM范围内。砷对土壤ACP的抑制作用主要受土壤有机质和阳离子交换容量的影响。这些因素影响了砷与酶的结合，从而导致砷对土壤ACP的毒性存在差异。土壤ACP的催化效率（V/K）是评估土壤砷污染生态风险的一个敏感动力学参数。
