EFFECTS OF PEBULATE AND PEBULATE SULFOXIDE ON VERY LONG-CHAIN FATTY-ACID BIOSYNTHESIS

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