Effects of pebulate and pebulate sulphoxide on very long chain fatty acid biosynthesis

The effects of the thiocarbamate herbicide, pebulate (S-propylbutylethylthiocarbamate) and its sulphoxide were investigated in vivo. The sulphoxide caused greater inhibition of very long chain fatty acid (VLCFA) synthesis from [1-C-14]acetate than pebulate, suggesting that the former was the physiologically-active form of the herbicide. In contrast, to fatty acid elongation, de:novo synthesis was insensitive to pebulate or its sulphoxide in vivo. The greater sensitivity of elongation to the sulphoxide was confirmed by in vitro assays which measured stearoyl-CoA or arachidoyl-CoA elongation with [2-C-14]malonyl-CoA. The results confirm suggestions that thiocarbamates are oxidised to their sulphoxide derivatives for full herbicidal activity and it is the latter which inhibit VLCFA and, hence, surface wax synthesis. (C) 1998 Elsevier Science Ltd. All rights reserved.