title: In vitro biotransformation of PBDEs by root crude enzyme extracts: potential role of nitrate reductase (NaR) and glutathione S-transferase (GST) in their debromination.
abstract: In order to investigate the enzyme transformation of PBDEs and to track the key enzymes involved in PBDE degradation in plants, in vivo exposure of plants of ryegrass, pumpkin and maize and in vitro exposure of their root crude enzyme extracts to PBDEs were conducted. Degradation of PBDEs in the root crude enzyme solutions fit well with the first order kinetics (R(2)=0.52-0.97, P<0.05), and higher PBDEs degraded faster than the lower ones. PBDEs could be transformed to lower brominated PBDEs and hydroxylated-PBDEs by the root crude enzyme extracts with debromination as the main pathway which contributed over 90% of PBDE depletion. In vitro and in vivo exposure to PBDEs produced similar responses in root enzyme activities of which the nitroreductase (NaR) and glutathione-transferase (GST) activities decreased significantly, while the peroxidase, catalase and cytochrome P-450 activities had no significant changes. Furthermore, higher enzyme concentrations of NaR and GST led to higher PBDE debromination rates, and the time-dependent activities of NaR and GST in the root crude enzyme extracts were similar to the trends of PBDE depletion. All these results suggest that NaR and GST were the key enzymes responsible for PBDE degradation. This conclusion was further confirmed by the in vitro debromination of PBDEs with the commercial pure NaR and GST.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
authors.forename: Honglin
authors.initials: H
authors.lastname: Huang
authors.forename: Shuzhen
authors.initials: S
authors.lastname: Zhang
authors.forename: Sen
authors.initials: S
authors.lastname: Wang
authors.forename: Jitao
authors.initials: J
authors.lastname: Lv
mesh_terms: D001673:Biodegradation, Environmental; D001711:Biotransformation; D005982:Glutathione Transferase / Q000378:metabolism*; D055768:Halogenated Diphenyl Ethers / Q000737:chemistry / Q000378:metabolism*; D054879:Halogenation; D050901:Nitrate Reductase / Q000378:metabolism*; D010936:Plant Extracts / Q000737:chemistry*; D010944:Plants / Q000378:metabolism*; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism*
chemical_list: D055768:Halogenated Diphenyl Ethers; D010936:Plant Extracts; D012989:Soil Pollutants; D050901:Nitrate Reductase; D005982:Glutathione Transferase