In situ susceptibilities of photosystem I and II to photosensitized inactivation via singlet oxygen mechanism
1993
Kim, C.S. | Han, G.H. | Kim, J.M. | Jung, J.
A comparative study was carried out on the in situ susceptibilities to photoinactivation of the photosystem I (PSI) and II (PSII) complexes of spinach thylakoids treated with efficient type II sensitizers. While the presence of the exogenous sensitizers caused a substantial increase in the extent of photoinactivation of whole chain electron transport, it did not affect PSI activity of thylakoids in light but exerted an enhanced photoinactivating effect only on PSII. The measurements of the action spectrum for the inhibition of PSII activity of the sensitizer-incorporated thylakoids and that for the generation of singlet oxygen (1O2) from them revealed that photosensitized inactivation of PSII is directly related to the photoproduction of O2 in thylakoid membranes. The results obtained in the present work clearly demonstrate an exceptional sensitivity of PS II to O2, Providing circumstantial evidence that high light-induced damage to PSII may result from photosensitization reactions mediated by 1O2, which is not necessarily produced within the PSII complex.
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