LIPID-PEROXIDATION IN PERIBACTEROID MEMBRANES FROM FRENCH-BEAN NODULES

Enriched peribacteroid membranes were prepared from Phaseolus vulgaris nodules and, in the presence of metleghemoglobin and H2O2, membranal lipid peroxidation was observed. The initial rate of the reaction was low and increased with time. Ferrous leghemoglobin was unable to induce this peroxidation with H2O2. Thus, it appears that leghemoglobin (IV) is not the activated species involved in this process. Heme plays a role in this peroxidation and the hydroxyl radical is not an intermediate of the reaction. Lipid peroxidation in peribacteroid membranes was also observed in the presence of iron ions. A mixture of iron (III) and iron (II) produced a maximal peroxidation. Senescing nodule extracts were able to provoke membranal lipid peroxidation; they contained nonprotein-bound iron. Peribacteroid membranes were more sensitive than microsomes to peroxidation, as measured by malonaldehyde formation.