Determination of NAD Malic Enzyme in Leaves of C4 Plants

摘要: Malate dehydrogenase may interfere with the assay of NAD malic enzyme, as NADH is formed during conversion malate to oxaloacetate. During present study, two additional effects were investigated; they are evident only if reaction allowed reach equilibrium prior initiating enzyme reaction. One these (Outlaw, Manchester 1980 Plant Physiol 65: 1136-1138) might cause an underestimation reduction by due oxidation reversal A second effect result in overestimation activity, Mn(2+)-catalyzed oxaloacetate decarboxylation causes continuing net formation via dehydrogenase. These studied assaying activity a partially purified preparation Amaranthus retroflexus presence or absence dehydrogenase.A model was developed which generation theoretical curves describing influence on activity. The experimental data obtained agreed closely curves. conditions included 5 millimolar malate, 2 NAD, and 4 Mn(2+) (pH 7.2 7.8 at 30 degrees C). At low activities (1 nanomole per minute milliliter less), leads substantial having dominant effect. When level greater than 1 milliliter, has transient effect, causing lag up several minutes, after change absorbance reflects true rate enzyme. Independent this activator-dependent rate, could be eliminated preincubating activator (coenzyme A).An procedure designed minimize described. New presented leaves different subgroups C(4) plants.