Peroxidase Isozymes from Horseradish Roots

Seven peroxidase isozymes were isolated from horseradish roots and purified to homogeneity as ascertained by chromatography, ultracentrifugation, and polyacrylamide disk electrophoresis. Purification procedures included ammonium sulfate precipitation and column chromatography on carboxymethyl and diethylaminoethyl cellulose. Peroxidase activity in the seven isozymes accounted for 86% of the activity in the crude homogenate. No interconversions among the isozymes were detected. The two most abundant isozymes were crystallized. The seven isozymes may be segregated into two groups on the basis of their chromatographic behavior, electrophoretic migration, spectrophotometric properties, and amino acid and carbohydrate composition. Each isozyme was shown to contain protohemin IX as the prosthetic group.