New aspects on inhibition of plant acetolactate synthase by chlorsulfuron and imazaquin

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Plant Physiology; (United States)

DOI:https://doi.org/10.1104/pp.95.4.1144· OSTI ID:5265153

Durner, J; Gailus, V; Boeger, P ^[1]

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1. Univ. Konstanz (West Germany)

The sulfonylurea herbicide chlorsulfuron and the imidazolinone herbicide imazaquin were shown to be noncompetitive and uncompetitive inhibitors, respectively, of purified acetolactate synthase from barley (Hordeum vulgare L.) with respect to pyrvuate. From double-reciprocal plots of the time-dependent biphasic inhibition by chlorsulfuron, and initial apparent inhibition constant of 68 nanomolar was calculated (a 0 to 4 minute assay was used for the initial inhibition), and a final steady-state dissociation constant of 3 nanomolar was estimated. The corresponding constants for imazaquin were 10 and 0.55 micromolar. Specific binding of ({sup 14}C)chlorsulfuron and ({sup 14}C)imazaquin to purified acetolactate synthase from barley and partially purified enzyme from corn (Zea mays L.) could be demonstrated by gel filtration and equilibrium dialysis. Evidence is presented that the binding of the inhibitors to the enzyme follows the previously described mechanism of slow reversibility once excess inhibitor has been removed. However, after formation of the slowly reversible complex and subsequent dissociation, both chlorsulfuron and imazaquin seem to permanently inactivate acetolactate synthase. These results add a new feature to the mode of action of these herbicides with respect to their high herbicidal potency.

• OSTI ID: 5265153
• Journal Information: Plant Physiology; (United States), Journal Name: Plant Physiology; (United States) Journal Issue: 4 Vol. 95:4; ISSN 0032-0889; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

551001* -- Physiological Systems-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BARLEY
BIOCHEMICAL REACTION KINETICS
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CARBON-CARBON LYASES
CEREALS
ENZYME ACTIVITY
ENZYMES
GRAMINEAE
HERBICIDES
INHIBITION
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
LILIOPSIDA
LYASES
MAGNOLIOPHYTA
MAIZE
PESTICIDES
PLANTS
REACTION KINETICS
TOXICITY
TRACER TECHNIQUES