E. Delfourne et al., SPECIFICITY OF PLANT ACETOHYDROXYACID SYNTHASE - FORMATION OF PRODUCTS AND INHIBITION BY HERBICIDES, Plant physiology and biochemistry, 32(4), 1994, pp. 473-477
Plant acetohydroxyacid synthase (EC 4.1.3.18) or AHAS catalyses either
the condensation of two molecules of pyruvate or one molecule of pyru
vate with one molecule of 2-ketobutyrate. 2-Aceto-2-hydroxybutyrate an
d 2-acetolactate are formed when the pyruvate concentration is ten tim
es greater than the 2-ketobutyrate concentration. This result indicate
s that plant AHAS has a preference for 2-ketobutyrate in the second su
bstrate site. A similar inhibition by sulfometuron methyl was observed
for the two reactions catalysed by the enzyme. These studies were dev
eloped by using a new chromatographic method based on the formation of
2,4-dinitrophenylhydrazone of acetoin and 2,4-dinitrophenyl-hydrazone
of 3-hydroxy-2-pentanone (compounds resulting of decarboxylation of t
he enzyme products).