Abstract
The purpose of this study was to clarify the subcellular localization of redox enzymes involving ascorbic acid in cucumber fruits. Subcellular fractions were prepared by differential centrifugation and sucrose density gradient centrifugation. From the determination of chlorophyll content and marker enzyme activities in each fraction, it was found that monodehydroascorbate reductase was contained in chloroplasts, mitochondria, microsomes, and cytosol. This enzyme was found not in broken chloroplasts but in intact ones. On the other hand, ascorbate oxidase was localized in microsomes and cytosol, and dehydroascorbate reductase was almost completely localized in cytosol.
Considering the ubiquitous distribution of monodehydroascorbate reductase in cucumber fruit cells, it is thought that this enzyme constitutes the main reducing system to regenerate ascorbic acid.
