Changes in the activity and isozyme patterns of malate dehydrogenase in root nodules of yellow lupine

The malate dehydrogenase present in the cytoplasmic fraction of plant origin and bacteroids from yellow lupine root nodules was investigated. The plant enzyme was 14 times more active in nodules than in roots and it contained 6 molecular forms in nodules compared with 3 forms detected in roots. The highest malate dehydrogenase activity in plant fraction and bacteroids was noted in 50-day old plants. Changes in the isoenzymatic patterns of malate dehydrogenase in plant fraction and bacteroids accompanying ageing of the lupine root nodules were observed. Possible physiological role of malate pathway in metabolism of lupine root nodules is discussed.