Effects of electron donor and acceptors, electron transfer mediators, and superoxide dismutase on lipid peroxidation in illuminated chloroplast fragments

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Effects of artificial electron donor and acceptors, electron transfer mediators, and superoxide dismutase on lipid peroxidation in illuminated chloroplast fragments were studied. An indicator of lipid peroxidation, malondialdehyde (MDA) formation, was stimulated by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). The DCMU-stimulated MDA formation was inhibited about 90% by reduced 2,6-dichloroindophenol (DCIP). In photosystem I-enriched particles, MDA formation was larger than that in normal chloroplast fragments on the chlorophyll basis. Benzyl viologen and ferredoxin stimulated DMA formation. Superoxide dismutase inhibited MDA formation strongly in the presence of benzyl viologen and weakly in its absence; the enzyme sometimes stimulated MDA formation in the presence of ferredoxin. Carbonylcyanide m-chlorophenylhydrazone (CCCP) stimulated MDA formation and maximal stimulation was attained at about 20 μl CCCP. Phenazine methosulfate, DCIP and benzoquinone inhibited MDA formation in the presence and absence of CCCP. From the above results, we confirmed our previous conclusion that most of the singlet molecular oxygen formed in illuminated chloroplasts is generated by electron transfer from O_2- to oxidized electron transfer components located, on the oxidizing sides of photosystems I and II.
日本植物生理学会の論文