Substrate Specificities of Peroxidase Isozymes in the Developing Pea Seedling

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Abstract
The peroxidase activities of developing pea seedlings were determined with several substrates including three phenolic compounds, eugenol, caffeic acid and ferulic acid, which are possible precursors in the biosynthesis of lignin. Column chromatography of the reaction products of peroxidase with caffeic and ferulic acids indicates the formation of larger molecular weight complexes of these substrates. The peroxidase isozymes of peas were shown to be heterogenous both in molecular weight and in substrate specificity. Apparent K m determinations of two isolated isozymes indicate differences in affinities for various substrates. Starch gel zymograms with two different substrates also indicate large differences in staining intensities of the different isozymes. The observed pattern of changes in peroxidase level in the developing pea seedling differed according to substrate. For example, when caffeic acid is the hydrogen donor, a large increase in activity was observed in the 6th to 8th day of germination. This peak of activity was not observed with other substrates.