Oxidation of Menadiol by Fractions Isolated From Non-Photosynthetic Plant Tissues

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Abstract
The oxidation of menadiol by fractions isolated from sweet potato roots and etiolated pea stems was examined using a spectrophotometric method. The mitochondria catalyze an O2-dependent menadiol oxidase reaction which is mediated in part, but not entirely, by the cytochrome system. The specific activity of the menadiol oxidase is approximately the same in all the cell fractions, and the bulk of the total activity is associated with the soluble fraction. The menadiol oxidase of the microsomal and soluble fractions is blocked by cyanide but is insensitive to antimycin A. The antimycin-insensitive menadiol oxidase is probably due to peroxidase acting as an aerobic oxidase. The intracellular localization of peroxidase activity is consistent with this possibility. The bulk of the DPNH-menadione reductase activity in the pea stem is associated with the soluble fraction, and the remainder is largely mitochondrial.