Altered feedback sensitivity to valine, leucine and isoleucine of acetolactate synthase from herbicide-resistant variants of Datura innoxia

Abstract

The activity of the enzyme, acetolactate synthase, extracted from cultured, wild-type cells of Datura innoxia P. Mill. was inhibited by valine and leucine (5–20 mM), added either separately or together, and by chlorsulfuron (10 −8 and 10 −5 M). Isoleucine (5–20 mM) was a weaker inhibitor than valine and leucine. Acetolactate synthase isolated from four chlorsulfuron-resistant, D. innoxia cell variants was also tested for feedback sensitivity to the three amino acids. Results showed that the acetolactate synthase from chlorsulfuron-resistant variants had less feedback sensitivity to valine, leucine and isoleucine added to assay mixtures either separately or in combination, compared to the enzyme from wild-type cells.