Dehydroascorbate reductase activity in bovine lens.

The bovine lens was studied for the presence of dehydroascorbate reductase activity. The activity was found to be restricted primarily to the mitochondrial fraction isolated from the cortex-epithelial fraction of the tissue. It was not detectable in the cytosolic fraction. The Km of reaction with dehydroascorbate was approximately 0.45 mM. These studies suggest that the reduction of dehydroascorbate to ascorbate in the mitochondria takes place enzymatically as well as nonenzymatically, GSH being the source of reducing electrons in both the cases. The enzymatic mechanism may assume a greater role in situations of oxidative stress which lead to GSH depletion. The presence of this enzyme in the mitochondria is considered with a normally more severe oxidative condition therein.