title: Inhibition of cytochromes P450 and the hydroxylation of 4-monochlorobiphenyl in whole poplar.
abstract: Cytochromes P450 (CYPs) are potential enzymes responsible for hydroxylation of many xenobiotics and endogenous chemicals in living organisms. It has been found that 4-monochlorobiphenyl (PCB3), mainly an airborne pollutant, can be metabolized to hydroxylated transformation products (OH-PCB3s) in whole poplars. However, the enzymes involved in the hydroxylation of PCB3 in whole poplars have not been identified. Therefore, two CYP suicide inhibitors, 1-aminobenzotriazole (ABT) and 17-octadecynoic acid (ODYA), were selected to probe the hydroxylation reaction of PCB3 in whole poplars in this work. Poplars (Populus deltoides × nigra, DN34) were exposed to PCB3 with or without inhibitor for 11 days. Results showed both ABT and ODYA can decrease the concentrations and yields of five OH-PCB3s in different poplar parts via the inhibition of CYPs. Furthermore, both ABT and ODYA demonstrated a dose-dependent relationship to the formation of OH-PCB3s in whole poplars. The higher the inhibitor concentrations, the lower the total yields of OH-PCB3s. For ABT spiked-additions, the total mass yield of five OH-PCB3s was inhibited by a factor of 1.6 times at an ABT concentration of 2.5 mg L(-1), 4.0 times at 12.5 mg L(-1), and 7.0 times at 25 mg L(-1). For the inhibitor ODYA, the total mass of five OH-PCB3s was reduced by 2.1 times compared to the control at an ODYA concentration of 2.5 mg L(-1). All results pointed to the conclusion that CYP enzymes were the agents which metabolized PCB3 to OH-PCB3s in whole poplars because suicide CYP inhibitors ABT and ODYA both led to sharp decreases of OH-PCB3s formation in whole poplars. A dose-response curve for each of the suicide inhibitors was developed.
authors: Department of Civil and Environmental Engineering and IIHR Hydroscience and Engineering, The University of Iowa, Iowa City, Iowa 52242, United States. zhai-guangshu@uiowa.edu
authors: Guangshu
authors: G
authors: Zhai
authors: Hans-Joachim
authors: HJ
authors: Lehmler
authors: Jerald L
authors: JL
authors: Schnoor
mesh_terms: D001713:Biphenyl Compounds / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004785:Environmental Pollutants / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D032107:Populus / Q000187:drug effects / Q000378:metabolism*; D014230:Triazoles / Q000494:pharmacology
chemical_list: D001713:Biphenyl Compounds; D065607:Cytochrome P-450 Enzyme Inhibitors; D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D014230:Triazoles; C033020:1-aminobenzotriazole; C047008:17-octadecynoic acid; D003577:Cytochrome P-450 Enzyme System; C006983:4-chlorobiphenyl