Alfalfa (Medicago sativaL. cv. Vernal) nodules were separated into host plant fractions and fractions of rhizobial origin by differential centrifugation and sedimentation equilibrium centrifugation. Both NAD- and NADP-linked isocitrate dehydrogenase (70%, 90%) and glutamate dehydrogenase activities (90%, 83%) were located primarily (percent total nodule activity) in the fractions of plant origin and their specific activities were highest in the fractions of plant origin. More than 50%of the nodules' total activity of both glutamine synthetase and NAD-glutamate synthase and greater than 90%of the total glutamate oxaloacetate transaminase activity was located in plant fractions. However, the fractions of rhizobial origin had the highest specific activities of glutamine synthetase and glutamate synthase.
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