N. Shiota et al., Expression of human cytochromes P450 1A1 and P450 1A2 as fused enzymes with yeast NADPH-cytochrome P450 oxidoreductase in transgenic tobacco plants, BIOS BIOT B, 64(10), 2000, pp. 2025-2033
Among 11 isoforms of the human cytochrome P450 enzymes metabolizing xenobio
tics, CYP 1A1 and CYP 1A2 were major P450 species in the metabolism of the
herbicides chlortoluron and atrazine in a yeast expression system. CYP1A2 w
as more active in the metabolism of both herbicides than CYP1A1, The fused
enzymes of CYP1A1 and CYP1A2 with yeast NADPH-cytochrome P450 oxidoreductas
e were functionally active in the microsomal fraction of the yeast Saccharo
myces cerevisiae and showed increased specific activity towards 7-ethoxyres
orufin as compared to CYP1A1 and CYP1A2 alone. Then, both fused enzymes wer
e each expressed in the microsomes of tobacco (Nicotiana tabacum cv, Samsun
NN) plants. The transgenic plants expressing the CYP1A2 fusion enzyme had
higher resistance to the herbicide chlortoluron than the plants expressing
the CYP1A1 fusion enzyme did, The transgenic plants expressing the CYP1A2 f
used enzyme metabolized chlortoluron to a larger extent to its non-phytotox
ic metabolites through N-demethylation and ring-methyl hydroxylation as com
pared to the plants expressing the CYP1A1 fused enzyme. Thus, the possibili
ty of increasing the herbicide resistance in the transgenic plants by the s
election of P450 species and the fusion with P450 reductase is discussed.