Cytoplasmic and Wall Isoperoxidases in Growing Maize Roots

Abstract

Cytoplasmic and wall-bound peroxidases (ionic and covalent) are extractable from maize roots (Zea mays L. cv. Orla 264). It is easier to extract ionic peroxidases when using divalent ions (Ca(+ +) and Mg(+ +))than monovalent ions (Na(+) and K(+)). The quantity of peroxidases extracted increases with the salt concentration. With 1M CaCl(2), the ionic peroxidases released from the walls increase during the ftrst hour. With cellulase and Drieselase, the covalent peroxidase released from the walls increases during the ftrst 8 hours and thereafter remains constant. Only the combination of the two enzymes was able to hydrolyze the wall efficiently. After disc gel electrophoresis and staining with 3-amino-9-ethyl carbazole, eleven bands were detected in the cytoplasmic fraction, four in the ionic wall-bound fraction (2, 3, 4, 6) and four in the covalent wall-bound fraction (2, 5, 6, 9). After selective extraction with dimethyl sulfoxide, a solvent of hemicellulose, and with Pectinol Fest (Polygalacturonase preparation) one isoperoxidase is shown to be associated with pectins, and another with the hemicellulose fraction. The isoperoxidases are not simultaneously incorporated in the walls where they undergo modifications. The presence of isoperoxidases in non lignified cell-walls, indicates that isoperoxidases control other processes that lignification.