Electrophoretic migration and redox behavior of malate dehydrogenases from cell suspension cultures of tobacco

Abstract

1. 1. The presence of one distinct mitochondrial malate dehydrogenase ( l-malate: NAD + oxidoreductase, EC 1.1.1.37), at least three cytosol malate (NAD +) dehydrogenase isoenzymes and only one cytosol malic enzyme component ( l-malate:NADP + oxidoreductase (decarboxylating), EC 1.1.1.40) were demonstrated in preparations from plant suspension cells cultivated at 25 °C. 2. 2. Bulk separation of the cytosol malate (NAD +) dehydrogenase isoenzymes was achieved by serial fractionation with (NH 4) 2SO 4. Each of the three enzyme forms possessed different kinetic properties and one of the isoenzymes did not require phenazine methosulfate to reduce tetrazolium after gel electrophoresis. 3. 3. Cultivating the plant suspension cells at temperatures at least 10 °C above or below 25 °C prevented expression of one or the other of three cytosol malate (NAD +) dehydrogenase isoenzymes. 4. 4. Treatment of the particulate preparation with deoxycholate increased the electrophoretic mobility of mitochondrial malate (NAD +) dehydrogenase. Depending on the concentration or assay method used, deoxycholate either inhibited or reversed the reaction catalyzed by soluble as well as particulate forms of malate (NAD +) dehydrogenase.