-transparent.png){kind=logo}
Acetohydroxyacid reductoisomerase was purified over 400-fold to a specific activity of 62 nkat.mg-1, with 2-aceto-2-hydroxybutyrate as substrate, from the stroma of spinach leaf chloroplasts. The enzyme was not intrinsically membrane bound. The native enzyme was a tetramer with a subunit Mr of 59,000. The activity was optimum between pH 7.5 and 8.5. The apparent Km for 2-acetolactate was 25 microM and for 2-aceto-2-hydroxybutyrate was 37 microM. The enzyme required Mg2+ and the Vmax. was attained at physiological Mg2+ concentrations. NADP+ competitively inhibited the reaction when NADPH was the varied substrate. The native enzyme eluted from Mono-Q ion-exchange resins as three distinct peaks of activity. This elution pattern was preserved when the peaks were combined, dialysed and re-chromatographed. Each form exhibited identical Mr of 59,000 after SDS/polyacrylamide gel electrophoresis (PAGE), whereas they were easily distinguishable from each other after PAGE under non-denaturing conditions. These results provide evidence for the existence of multiple forms of acetohydroxyacid reductoisomerase in chloroplasts isolated from spinach leaves.
R Dumas, and
J Joyard, and
R Douce
June 1992,
Archives of biochemistry and biophysics,
R Dumas, and
J Joyard, and
R Douce
July 1991,
The Biochemical journal,
R Dumas, and
J Joyard, and
R Douce
December 1979,
Biochimica et biophysica acta,
R Dumas, and
J Joyard, and
R Douce
July 2000,
Plant & cell physiology,
R Dumas, and
J Joyard, and
R Douce
September 1985,
Plant physiology,
R Dumas, and
J Joyard, and
R Douce
February 1974,
Biochimica et biophysica acta,
R Dumas, and
J Joyard, and
R Douce
September 1985,
Planta,
R Dumas, and
J Joyard, and
R Douce
January 1982,
The Journal of biological chemistry,
R Dumas, and
J Joyard, and
R Douce
June 1990,
Plant physiology,
R Dumas, and
J Joyard, and
R Douce
January 1988,
Photosynthesis research,
