CA2-CALMODULIN-STIMULATED SUPEROXIDE GENERATION BY PURIFIED PLASMA-MEMBRANE FROM WHEAT ROOTS()

Highly purified plasma membranes were isolated by aqueous two-phase pa rtitioning from wheat roots. The superoxide generation was studied by EPR technique with Tiron as the spin trap. Ca2+-calmodulin could stimu late the TH signal, while SOD and several calmodulin antagonists, La3, EGTA and CPZ could inhibit the TH signal. Stimulation of TH signal b y Ca2+-calmodulin was dependent on NADH and calmodulin. The above resu lts provided direct evidence for the connection of calmodulin to the r edox system of plasma membranes. Similarly, catalase and KCN could als o inhibit TH signal. No stimulation of superoxide production was obser ved when Ca2+ and calmodulin were added separately. NADPH could not el icit TH signal in the study of the stimulation of superoxide by Ca2+-c almodulin. Triton X-100 (0.05%) could not cause a significant increase in TH. signal.