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Ecotoxicol Environ Saf. 2018 Jan;147:266-274. doi: 10.1016/j.ecoenv.2017.08.050. Epub 2017 Sep 14.

Soil properties influence kinetics of soil acid phosphatase in response to arsenic toxicity.

Author information

1
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.
2
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.
3
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. Electronic address: wenxiang.he@nwafu.edu.cn.

Abstract

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 (Km) and maximum reaction velocity (Vmax) values of soil ACP ranged from 1.18 to 3.77mM and 0.025-0.133mMh-1 in uncontaminated soils. The kinetic parameters of soil ACP in different soils changed differently with As contamination. The Km remained unchanged and Vmax decreased with increase of As concentration in most acid and neutral soils, indicating a noncompetitive inhibition mechanism. However, in alkaline soils, the Km increased linearly and Vmax decreased with increase of As concentration, indicating a mixed inhibition mechanism that include competitive and noncompetitive. The competitive inhibition constant (Kic) and noncompetitive inhibition constant (Kiu) 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 (Vmax/Km) of soil ACP was a sensitive kinetic parameter to assess the ecological risks of soil As contamination.

KEYWORDS:

Arsenic; Inhibition constant; Noncompetitive inhibition; Soil acid phosphatase; Soil property

PMID:
28850809
DOI:
10.1016/j.ecoenv.2017.08.050
[Indexed for MEDLINE]

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