Comparison of the biotransformation of the 14C-labelled insecticide carbaryl by non-transformed and human CYP1A1-, CYP1A2-, and CYP3A4-transgenic cell cultures of Nicotiana tabacum.
Transgenic tobacco-cell-suspension cultures expressing separately the human cytochrome P450 monooxygenases CYP1A1, CYP1A2, and CYP3A4 were utilized to study the biotransformation of the 14C-labelled insecticide carbaryl (=naphthalen-1-yl methylcarbamate). The resulting data were compared to similar data from the corresponding non-transformed (NT) tobacco-cell culture and commercially available membrane preparations (Bactosomes) of genetically modified bacteria separately containing the same human P450s. A rapid conversion rate of carbaryl was observed with the CYP1A1 and CYP1A2 cells, where only 49.7 and 0.2% of applied carbaryl (1 mg/l), respectively, remained after 24 h, as compared to 77.7% in the non-transformed culture. Unexpectedly, the corresponding results obtained from the CYP3A4 cultures were not definite. With 25 mg/l of carbaryl and 96 h of incubation, it was proven that the insecticide is also substrate of CYP3A4. This finding was supported by GC/EI-MS analysis of the primary metabolite pattern produced by the isozyme. This consisted of naphthalene-1-ol, N-(hydroxymethyl)carbaryl, 4-hydroxycarbaryl, and 5-hydroxycarbaryl, whereas the main product in non-transformed cells was N-(hydroxymethyl)carbaryl. Data obtained from the CYP1A1, CYP1A2, or CYP3A4 Bactosomes agreed with those of the P450-transgenic tobacco cells. Problems with GC/EI-MS analysis of carbaryl and its metabolites are discussed.
Schmidt
Burkhard
B
Institute of Biology V, Chair: Ecology/Ecotoxicology/Ecochemistry, RWTH Aachen University, Worringerweg 1, D-52056 Aachen. burkhard.schmidt@post.rwth-aachen.de
Faymonville
Tanja
T
Gembé
Eva
E
Joussen
Nicole
N
Schuphan
Ingolf
I
D012721:Carbaryl / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000737:chemistry; D002457:Cell Extracts; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism*; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D006868:Hydrolysis; D007306:Insecticides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D015394:Molecular Structure; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*
D002250:Carbon Radioisotopes; D002457:Cell Extracts; D007306:Insecticides; D003577:Cytochrome P-450 Enzyme System; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D012721:Carbaryl