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

The role of quinones in electron transport has attracted considerable recent interest (27). Coenzyme Q1O, which is present in plant mitochondria, is closely related to the respiratory chain (6), and the very similar benzoquinone, plastoquinone, appears to be involved in photosynthesis (7) Vitanmin K-type naphthoquinones have been imlplicated in respiratory electron transfer (30), oxidative phosphorylation (2), and photophosphorylation (1). The enzymatic pathways involved in the intracellular oxidation and re(luction of these quinones are clearly of interest. Wosilait an(l Nason (32) showed that extracts of animiials, plants, and bacteria contain an active pyridine nucleotide-menadione (vitamiin K;) reductase, andl since then a number of enzymles which catalyze the re(luction of naphtlhoquinones an(I benzoquinones or benzoquinones alone have been purified. The pathways of oxidation of the reduce(d quinones have also been examined, though most of the work has been (lone with animal systemls (8. 9, 22). This aspect of the problem is of special interest in plants, since, in addition to the usual respiratory chain, they contain a number of enzymes (phenol oxidase, laccase, peroxidase) which can oxidlize phenols to their corresp,onding quinones. In the present study. we have used menadiol andl mlenla(lionie as moclel comilpoun(ls and have examined their oxidationi andl redluction by cell-free fractions isolated froml non-photosynthetic tissues. Special attention has been paidI to the intracellular localization of these activities and to the components involved in the oxidative pathways.