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KINETIC PROPERTIES OF MALIC DEHYDROGENASE FROM THREE CULTIVARS OF RICE
Citation:
Snow, M. AND R. Bard. KINETIC PROPERTIES OF MALIC DEHYDROGENASE FROM THREE CULTIVARS OF RICE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-92/074.
Description:
Temperature induced changes in the kinetics of the enzyme malic dehydrogenase (MON) were investigated in three cultivars of rice(Oryza sativa L.). Cultivars, included IR74, SWAT2, and N22. Plants were grown in a controlled environment chamber for 29 days, at 31 degrees C day/25 degrees C night. nzyme extracts were assayed for MDH activity by following the oxidation of NADH Spectrophotometrically at 340nm. ssays were performed using seven substrate concentrations of oxaloacetic acid ranging from 2.0mM to 0.05mM at temperatures ranging from 15 to 35 degrees C. Apparent Km, Km/Vmax, activation energies, and enzyme activities were computed. esults showed an increase in apparent Km with temperature for all cultivars. nergies of activation were higher than those reported for MDH in other plant species at similar acclimation temperatures. 22, an upland cultivar with both heat and drought tolerance, had significantly higher energies of activation than other cultivars. m/Vmax ratios indicated that substrate binding varied with temperature. WAT2, a cold tolerant, lowland cultivar, showed maximum substrate binding over the lowest range of temperatures. esults indicate that some of these kinetic parameters may be useful indicators of temperature adaptations among rice cultivars.