부산대학교 도서관

Auxin-oxidasic activity, peroxidase, catalase and phenoloxidase have been comparatively studied in extracts from beans' roots and hypocotyls cultivated in the dark or in the light. Furthermore, the effectors' capacity of these extracts has been investigated — after boiling — on the activity of purified peroxidase, catalase and phenoloxidase, in their own property and in their respective capacity to oxidize IAA. Beans' extracts show IAA-oxidase, peroxidase and catalase but not phenoloxidase; they also contain effectors of peroxidase and catalase, respectively in their property to oxidize phenols and to decompose hydrogen peroxide and in their property to destroy IAA too. No trace of phenoloxidasic effectors is detected so that phenol-oxidase does not seem to be present. Auxin-oxidasic activity is diminished when Phaseolus is cultivated in the light: cinetic curves indicate that this diminution is due to a light induced increase in natural inhibitors of the enzymic auxin degradation. Because the extracts from the light cultivated beans are more inhibitory of the auxin catabolism by a purified peroxidase (horseradish) and by a purified catalase (bovin liver) than extracts from the dark cultivated ones, it is concluded that peroxidase and catalase at least participate to auxin destruction by Phaseolus extracts. Purified tyrosinase (mushroom) does not catalyse IAA destruction. The copper nature of the enzymic IAA degradation proposed by Wagenknecht et Burris (1950) is discussed. Light not only modifies the effectors metabolism of peroxidase and catalase when they attack IAA but also when they oxidize phenols or decompose hydrogen peroxide. Phenols and hydrogen peroxide have an important action in auxin degradation. Thus there is possibility of a new pathway of the light action on auxin catabolism in vivo.