title: Effects of metal ions on the catalytic degradation of dicofol by cellulase.
abstract: A new technique whereby cellulase immobilized on aminated silica was applied to catalyze the degradation of dicofol, an organochlorine pesticide. In order to evaluate the performance of free and immobilized cellulase, experiments were carried out to measure the degradation efficiency. The Michaelis constant, Km, of the reaction catalyzed by immobilized cellulase was 9.16 mg/L, and the maximum reaction rate, Vmax, was 0.40 mg/L/min, while that of free cellulase was Km=8.18 mg/L, and Vmax=0.79 mg/L/min, respectively. The kinetic constants of catalytic degradation were calculated to estimate substrate affinity. Considering that metal ions may affect enzyme activity, the effects of different metal ions on the catalytic degradation efficiency were explored. The results showed that the substrate affinity decreased after immobilization. Monovalent metal ions had no effect on the reaction, while divalent metal ions had either positive or inhibitory effects, including activation by Mn2+, reversible competition with Cd2+, and irreversible inhibition by Pb2+. Ca2+ promoted the catalytic degradation of dicofol at low concentrations, but inhibited it at high concentrations. Compared with free cellulase, immobilized cellulase was affected less by metal ions. This work provided a basis for further studies on the co-occurrence of endocrine-disrupting chemicals and heavy metal ions in the environment.
authors.affiliation: Collaborative Innovation Center for Regional Environmental Quality, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Science and Engineering, Peking University, Beijing 100871, China.
authors.forename: Zihan
authors.initials: Z
authors.lastname: Zhai
authors.affiliation: Collaborative Innovation Center for Regional Environmental Quality, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Science and Engineering, Peking University, Beijing 100871, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Yang
authors.affiliation: School of Public Health, Peking University, Beijing 100191, China.
authors.forename: Boya
authors.initials: B
authors.lastname: Zhang
authors.affiliation: Collaborative Innovation Center for Regional Environmental Quality, State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Science and Engineering, Peking University, Beijing 100871, China. Electronic address: jbzhang@pku.edu.cn.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Zhang
mesh_terms: D002480:Cellulase / Q000737:chemistry / Q000378:metabolism*; D004010:Dicofol / Q000737:chemistry / Q000378:metabolism*; D004785:Environmental Pollutants / Q000737:chemistry; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008670:Metals / Q000494:pharmacology*; D010575:Pesticides / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004785:Environmental Pollutants; D004800:Enzymes, Immobilized; D008670:Metals; D010575:Pesticides; D002480:Cellulase; D004010:Dicofol
keywords: Catalytic degradation; Cellulase; Dicofol; Immobilization; Metal ions