Cadmium induced changes in cell wall peroxidase isozyme pattern in barley root tips

Changes in peroxidase activity as well as isozyme peroxidase pattern were analyzed in five cell wall (CW) fractions of barley roots exposed to 1mM CdCl2 for 48 and 72 h. Whereas strong inhibition of peroxidase activity was detected in fraction CW I and weak inhibition in fractions CW II, III and IV, strong activation of peroxidase was observed in fraction V after Cd application. Despite the inhibition of enzyme activity in most CW fractions, induction of several isoperoxidases was discovered after separation on PAGE. In fraction CW I inhibition of one cathodic isoperoxidase and activation of two anodic and two cathodic isoperoxidases was detected. Additional two anodic and one cathodic Cd-induced isozyme appeared in CW II and CW III. Strongly activated anodic isoperoxidase was detected in fraction CW V. Our results demonstrate that monitoring the stress modified peroxidase activity in enzyme extracts using guaiacol as a non-specific peroxidase substrate is not sufficient enough. Since some isozymes can be activated and some inhibited, isozyme pattern analysis is recommended.