INVESTIGATIONS OF ASCORBIC ACID DEHYDROGENASE OF PEAS (PISUM SATIVUM) AND ITS DISTRIBUTION IN THE DEVELOPING PLANT

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Abstract
Ascorbic acid dehydrogenase, also called dehydroascorbic acid reductase and ascorbic reductase, catalyzes the reduction of dehydro-ascorbic and with glutathione as the substrate producing ascorbic acid and oxidized glutathione. The enzyme was extracted from fresh peas at O[degree]C. The activity was measured in Thunberg tubes under anaerobic conditions. The amt. of ascorbic acid produced, detd. colorimetrically, was taken as a measure of enzyme activity. The opt. pH was 6.9 in phosphate buffer. This enzyme was most active in phosphate buffers and gave low activities in metaphosphate, citrate and acetate buffers of the same strength. This enzyme was stable at lower temps. but was easily inactivated at higher temps. In germinating pea seeds the embryo had the highest dehydrogenase activity and the activity in the cotyledons decreased from a fairly high value at beginning to just a trace after 28 days. The growing point and leaves had high enzyme activity. The youngest pea seeds had the highest activity. The pea pods were very low in dehydrogenase content.