الفهرس Only 14 pages are availabe for public view
 |  | from | 183 |  |  |
| | | from | 183 | | |
Abstract
Weed control by herbicides has helped us to create the green
revolution and to provide food for at least the majority of human beings living today. However, some herbicides remain in the environment and pose an ecological problem.
Cytochromes P450 are ubiquitously distributed enzymes, which possess high complexity and display a broad field of activity. They are hemoproteins converting a broad variety of substrates and catalyzing a variety of interesting chemical reactions. This enzyme family is involved in the biotransformation of drugs, as well as the degradation of herbicides and insecticides.
The first aim of the present work was to examine the catalytic activity of the human P450 isozymes CYP1A1, CYP1A2 and CYP3A4 expressed in tobacco cell cultures regarding the herbicide simazine.
First, metabolism studies were executed with 14C-labelled simazine using non-transgenic and Cyp1a1-, Cyp1a2- and Cyp3a4- transgenic tobacco cell cultures available at the institute. According to HPLC analysis, the results proved that simazine was completely metabolized by the Cyp1a2-transgenic culture via N- dealkylation with successive loss of both ethyl groups resulting in 2-chloro-4-(ethylamino)-6-amino s-triazine, DeS, and 2-chloro-4,6-diamino-s-triazine, DiDeS, which are prevailingly nonphytotoxic metabolites. The herbicide was biotransformed to a minor extent in the non-transgenic cells to metabolites with residual phytotoxicity. Cyp1a1- and Cyp3a4- transgenic cultures showed a lower capacity for simazine metabolism than the Cyp1a2-transgenic and a higher than the non-transgenic cells.