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

Abstract

Ascorbic acid has long been considered as a possible hydrogen donor in the intermediary oxidation-reduction chain in living tissues. The biological oxidation of ascorbic acid to dehydro-ascorbic acid by ascorbic acid oxidase, polyphenolase, peroxidase, and other systems has been carefully worked out by many investigators (?4). In plants, however, ascorbic acid is nearly always found in the reduced state and very little is found as dehydroascorbic acid, the oxidized state. Therefore there must be present in the living plant cells some reducing mechanism to maintain the ascorbic acid in the reduced state in spite of the terminal oxidases and oxidizing catalysts which tend to oxidize it to dehydro-ascorbic acid. Recently several investigators (5, 9, 15, 16) have reported that such an enzyme exists in peas. The enzyme, ascorbic acid dehydrogenase, also called dehydro-ascorbic acid reductase and ascorbic reductase, catalyzes the reduction of dehydro-ascorbic acid as given in the following equation: