To obtain information on differences between the metabolic pathways of the herbicide
glufosinate (trade names: BASTA®, LIBERTY®) in non-transgenic, glufosinate-sensitive
plants and in transgenic, glufosinate-resistant plants, the metabolism of
14C-labeled glufosinate and its enantiomers L- and D-glufosinate was studied
using cell cultures of oilseed rape and corn. Transformation of glufosinate in
both sensitive and transgenic rape cells remained at a low rate of about 3-10%
in contrast to corn cells, where 20% was transformed in sensitive and 43% in
transgenic cells after 14 days of incubation, the rest remaining as unchanged
glufosinate. In sensitive rape and corn cells the main metabolite was
4-methylphosphinico-2-oxo-butanoic acid (PPO) with 7.3 and 16.4%,
respectively, together with low amounts of 3-methylphosphinicopropionic
acid (MPP), 4-methylphosphinico-2-hydroxybutanoic acid (MHB),
4-methylphosphinicobutanoic acid (MPB) and 2-methylphosphinicoacetic acid (MPA).
An additional metabolite formed in transgenic cell cultures was
2-acetamido-4-methylbutanoic acid (N-acetyl-L-glufosinate, NGA), which was
formed at rates of 3.2% in rape and 16.1% in corn. A further minor metabolite,
not yet identified, was detected in both cell types. The liberation of 0.2% 14CO2
indicates further metabolic steps prior to a limited mineralization in plant cell
cultures. L-glufosinate was transformed into the same metabolites as the
glufosinate racemate. D-glufosinate was not metabolized.