INHIBITION OF THREONINE DEHYDRATASE IS HERBICIDAL

Threonine dehydratase, the first enzyme in isoleucine biosynthesis, ca talyzes deamination and dehydration of threonine to produce 2-ketobuty rate and ammonia. An antimetabolite, 2-(1-cyclohexen-3(R)-yl)-S-glycin e (CHG), inhibits the plant enzyme. CHG inhibits the growth of Black M exican Sweet corn (Zea mays) cells and of Arabidopsis thaliana plants. The herbicidal effects of CHG can be reversed by 2-ketobutyrate, othe r intermediates of isoleucine biosynthesis, and by isoleucine itself. These results suggest that the herbicidal effects observed with CHG ar e a consequence of inhibition of threonine dehydratase. The enzyme cou ld be a potential target site for an herbicide screening program.