title: Potential enzyme toxicity of oxytetracycline to catalase.
abstract: Oxytetracycline (OTC) is a kind of widely used veterinary drugs. The residue of OTC in the environment is potentially harmful. In the present work, the non-covalent toxic interaction of OTC with catalase was investigated by the fluorescence spectroscopy, UV-vis absorption and circular dichroism (CD) spectroscopy at physiological pH 7.4. OTC can interact with catalase to form a complex mainly by van der Waals' interactions and hydrogen bonds with one binding site. The association constants K were determined to be K(293K)=7.09×10(4)Lmol(-1) and K(311K)=3.31×10(4)Lmol(-1). The thermodynamic parameters (ΔH°, ΔG° and ΔS°) of the interaction were calculated. Based on the Förster theory of non-radiative energy transfer, the distance between bound OTC and the tryptophan residues of catalase was determined to be 6.48nm. The binding of OTC can result in change of the micro-environment of the tryptophan residues and the secondary structure of catalase. The activity of catalase was also inhibited for the bound OTC. This work establishes a new strategy to probe the enzyme toxicity of veterinary drug residues and is helpful for clarifying the molecular toxic mechanism of OTC in vivo. The established strategy can be used to investigate the potential enzyme toxicity of other small organic pollutants and drugs.
authors.affiliation: School of Environmental Science and Engineering, Shandong University, China-America CRC for Environment & Health, Shandong Province, 27# Shanda South Road,Jinan 250100, PR China.
authors.forename: Zhenxing
authors.initials: Z
authors.lastname: Chi
authors.forename: Rutao
authors.initials: R
authors.lastname: Liu
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000633:toxicity*; D002374:Catalase / Q000737:chemistry* / Q000633:toxicity; D004347:Drug Interactions; D004735:Energy Transfer; D004785:Environmental Pollutants / Q000737:chemistry / Q000633:toxicity*; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D010118:Oxytetracycline / Q000737:chemistry / Q000633:toxicity*; D019155:Veterinary Drugs / Q000737:chemistry / Q000633:toxicity
chemical_list: D000900:Anti-Bacterial Agents; D004785:Environmental Pollutants; D019155:Veterinary Drugs; D002374:Catalase; D010118:Oxytetracycline