4‐Methoxy‐α‐naphthol as a specific substrate for kinetic, zymographic and cytochemical studies on plant peroxidase activities

Abstract

Abstract A new and sensitive chromogenic assay has been developed to characterize peroxidative activities in plant tissues, applicable to kinetic, zymographic and cytochemical studies on plant peroxidases. This technique is based on the H 2 O 2 ‐dependent oxidation of 4‐methoxy‐α‐naphthol (4‐MN) to yield a non‐diffusable deep‐blue product, the appearance of which is kinetically correlated with the disappearance of 4‐MN. Oxidation conditions have been optimized. Since 4‐MN is a specific substrate for peroxidase against other heme proteins (catalase and cytochrome c) and, because of the high sensitivity and low detection limit of peroxidase activity in the 4‐MN assay, this compound is a powerful reagent in the study of peroxidase activity from plant tissues. The assay has been applied to the kinetic, zymographic and cytochemical characterization of peroxidase activity in grape cell cultures.