Participation of Cytochrome Oxidase in Lignification

Abstract

INVESTIGATIONS during recent years on the more exact characterization of ‘redoxases’ involved in the lignification process have led, in the first instance, to the suggestion that this enzyme may be a laccase¹. But since the distribution of laccase is principally restricted to lower plants, the consideration of laccase as the sole dehydrogenating enzyme in the formation of lignin cannot be accepted. Siegel^2,3 especially directed attention to another enzyme, namely, peroxidase. This enzyme can form lignin-like products from eugenol in the presence of hydrogen peroxide. Hence it is quite possible that also in vivo in the zone of lignification of a woody plant, peroxidase is an essential part of the mechanism of lignification. In fact, investigations of Wardrop and Bland⁴ on the topological distribution of peroxidase by means of benzidine/hydrogen peroxide in the lignification zone have shown a positive reaction in the cambium cells and in the walls of the first dividing xylem cells, but as soon as a lignification did occur, peroxidase could no longer be detected.