Both glutathione and an NADPH-dependent glutathione reductase are present in spinach (Spinacia oleracea L.) chloroplasts. It is proposed that glutathione functions to stabilise enzymes of the Calvin cycle, and it may also act to keep ascorbic acid in chloroplasts in the reduced form.

The presence of glutathione and glutathione reductase in chloroplasts: A proposed role in ascorbic acid metabolism.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2881%2980729-6

Ascorbate free radical reductase, a key enzyme of the ascorbic acid system

By using lycorine, a specific inhibitor of ascorbate biosynthesis, it was possible to demonstrate that plant cells consume a high quantity of ascorbate (AA). Thein vivo metabolic reactions utilizing ascorbate are the elimination of H2O2 by ascorbate peroxidase and the hydroxylation of proline residues present in the polypeptide chains by means of peptidyl-proline hydroxylase.

Ascorbate system in plant development

Metabolic reactions to auxin I The effects of auxin on glutathione and the effects of glutathione on growth of isolated plant parts

Dehydroascorbate-reducing proteins in maize are induced by the ascorbate biosynthesis inhibitor lycorine

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:

M. Yamaguchi

Papers

Peas (pisum sativum) and its distribution in the developing plant