Activated oxygen generation from thylakoids: a novel spin trap.
Using a novel phosphorylated spin trap, 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), an analogue of the commonly used spin trap 5,5'-dimethyl-1-pyrroline N-oxide (DMPO), we have investigated the production of oxygen radical species under illumination of thylakoids from wheat (Triticum durum Desf cv. Ofanto). DEPMPO reacted with superoxide (O2*-) and hydroxyl radical (HO*) forming distinctive spin trap adducts. Spectra of (O2*-) and HO* adducts of DEPMPO were recorded in the presence of xanthine/xanthine oxidase and FeSO4/H2O2, respectively, and computer simulation of spectra was performed. During illumination of thylakoids both O2*- and HO* were detected as well. Transition metals catalysed transformation of O2*- into HO*. The conversion was enhanced by H2O2 and prevented by exogenous superoxide dismutase and catalase. The presence of a thylakoid-bound superoxide dismutase, whose activity was inhibited by H2O2 and diethyldithiocarbamic acid, was responsible for H2O2 production from O2*- and thus for HO* generation.
Sgherri
C L
CL
Dipartimento di Chimica e Biotecnologie Agrarie, Università degli Studi di Pisa, Italy.
Pinzino
C
C
Samaritani
E
E
Navari-Izzo
F
F
D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D017665:Hydroxyl Radical / Q000378:metabolism; D008027:Light; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013113:Spin Labels; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism* / Q000528:radiation effects; D014908:Triticum / Q000378:metabolism* / Q000528:radiation effects
D003497:Cyclic N-Oxides; D017382:Reactive Oxygen Species; D013113:Spin Labels; D013481:Superoxides; C098505:5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide; D017665:Hydroxyl Radical; D013482:Superoxide Dismutase