SOME PROPERTIES OF PEROXIDASE PRODUCED IN SWEET POTATO INFECTED BY THE BLACK ROT FUNGUS1

Abstract

Chemical and physicochemical properties of peroxidases produced back rotted sweet potato roots were investigated in comparison with those produced in cut one. Peroxidases in either diseased or cut tissue were composed of four major (D-A, D-B, D-C and D-D in diseased tissue and C-A, C-B, C-C and C-D in cut tissue) and several minor components. These peroxidases were separated from each other by DEAE-cellulose column chromatography and other procedures. Several properties of the peroxidases were investigated. Peroxidase A (D-A), the main component in diseased tissue, was purified by methods such as DEAE-cellulose chromatography and starchgel electrophoresis to a grade higher than previously shown. It was homogeneous, according to investigations with ultracentrifugation, immunochemical reaction and starch-gel electrophoresis. Pyridine hemochrome of the peroxidase showed that the heme in it was protoheme. Amino acid composition of the enzyme was determined. Peroxidase A oxidized various phenolic substances in the presence of H₂O₂. Indoleacetic acid oxidase activity of peroxidase A was inhibited by both chlorogenic acid and guaiacol.