Mn(II)-Mn(III)-Mn(IV) redox cycling inhibits the removal of methylparaben and acetaminophen mediated by horseradish peroxidase: New insights into the mechanism

Zhimin Gong; Gaobo Wang; Huanhuan Shi; Shuai Shao; Mengjie Wang; Kun Lu; Shixiang Gao

doi:10.1016/j.scitotenv.2021.147788

Mn(II)-Mn(III)-Mn(IV) redox cycling inhibits the removal of methylparaben and acetaminophen mediated by horseradish peroxidase: New insights into the mechanism

Sci Total Environ. 2021 Sep 20:788:147788. doi: 10.1016/j.scitotenv.2021.147788. Epub 2021 May 15.

Authors

Zhimin Gong¹, Gaobo Wang², Huanhuan Shi³, Shuai Shao¹, Mengjie Wang¹, Kun Lu⁴, Shixiang Gao⁵

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China.
² School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of Ministry of Education, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing 210093, PR China.
³ School of Ecology and Environment, Zhengzhou University, Zhengzhou 450001, PR China.
⁴ State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China. Electronic address: kunlu@nju.edu.cn.
⁵ State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China. Electronic address: ecsxg@nju.edu.cn.

PMID: 34029809
DOI: 10.1016/j.scitotenv.2021.147788

Abstract

Catalyzed oxidative coupling reactions mediated by enzyme have been proposed as an effective remediation strategy to remove micropollutants, however, little is known about how the Mn(II) redox cycling affects the horseradish peroxidase (HRP)-mediated reactions in wastewater treatment. Here, we explored the removal of two pharmaceuticals and personal care products (PPCPs), methylparaben (MeP) and acetaminophen (AAP), in HRP-mediated reaction system with dissolved Mn (II). It was found that the conversion rate of AAP was about 284 times higher than that of MeP, and Mn (II) significantly inhibited HRP-catalyzed MeP removal but had little influence on that of AAP. X-ray photoelectron spectroscopy (XPS) and theoretical calculations demonstrated that HRP converted Mn(II) into Mn(III), and then generated MnO₂ colloid, which inhibited the removal of the substrates. Moreover, the results of theoretical calculations also showed that the binding energy between HRP and Mn was 27.68 kcal/mol, which was higher than that of MeP (25.24 kcal/mol) and lower than that of AAP (30.19 kcal/mol). Therefore, when MeP and Mn (II) coexisted in the reaction system, HRP preferentially reacted with Mn(II), which explained the different impacts of Mn (II) on the removal of MeP and AAP. Additionally, Mn (II) significantly altered the product distribution by decreasing the amount of polymerization products. Overall, our work here revealed the roles of Mn (II) in the removal of MeP and AAP mediated by HRP, having strong implications for an accurate assessment of the influence of Mn(II) redox cycling on the removal of PPCPs in wastewater treatment.

Keywords: Enzyme-mediated; Inhibition mechanism; Mn(II) redox cycling; PPCPs; Theoretical calculations.

MeSH terms

Acetaminophen*
Horseradish Peroxidase / metabolism
Manganese Compounds*
Oxidation-Reduction
Oxides
Parabens

Substances

Manganese Compounds
Oxides
Parabens
Acetaminophen
methylparaben
Horseradish Peroxidase