A COMPARATIVE STUDY OF NITRATE REDUCTION AND THE OXIDATION OF GLYCOLATE

ABSTRACT Activity of nitrate reductase and glycolate dehydrogenase in spinach leaves changes in identical patterns following changes in the levels of nitrate available in the nutrient solution of the plants. Replacing nitrate by ammonium ions caused loss of activity of both enzymes in cauliflower but this loss was less extensive in spinach plants. Glycolate dehy drogenase and nitrate reductase activities were negligible in Mo-deficient spinach and cauliflower leaves, but increased to identical extents upon addition of Mo to the nutrient medium. The activity of both enzymes was increased to levels found in control plants when tungstate was added to Mo-deficient plants. Phosphate buffer was found to be the best extraction medium for both enzymes, stimulating nitrate reductase by 15% and glycolate dehydrogenase 3-fold. Both enzymes showed a similar pH sensitivity but differed in their thermal denaturation activation energies. Gel chromatography indicated that glycolate dehydrogenase protein differs from that...