A colorimetric method for the determination of peroxidase in plant material.

In a previous paper (1) a calorimetric phenol oxidase method was presented which utilizes catechol as a mediator and in which the oxidation of a leucoindophenol is followed photometrically over a very short time interval. During the development of this method it was found that the same basic method and technique were applicable to the determination of peroxidase. In the latter case, oxidation of the leucoindophenol dye is catalyzed directly by peroxidase in the presence of hydrogen peroxide. Since it is often desirable to determine both phenol oxidase and peroxidase in a given plant material, a basically similar method for both enzymes was considered advantageous. Most previous peroxidase methods have also been calorimetric and have utilized a variety of oxygen acceptors such as pyrogallol (24), leucomalachite green (5, 6), guaiacol (6), nadi reagent (7), and others. Lucas and Bailey (8) have also used an indophenol dye similar to that in the present work, but in a quite different way. Another method commonly used, especially in the assay of plant material, is that of Balls and Hale (9), in which pyrogallol is the oxygen acceptor, but the utilization of hydrogen peroxide is measured. This paper includes (a) a brief discussion of factors involved in the proposed calorimetric reaction and in the enzyme preparation, (b) a description of the method adopted, (c) some results of its application to plant materials, and (d) some points of comparison with other methods.