ACTION SPECTRA FOR THE GENERATION OF SINGLET OXYGEN FROM MITOCHONDRIAL-MEMBRANES FROM SOYBEAN (GLYCINE-MAX) HYPOCOTYLS

Abstract— The action spectrum for the generation of singlet oxygen (1O2) from mitochondrial membranes under aerobic conditions was measured at wavelengths between 360 and 600 nm, using sub‐mitochondrial particles (SMP) prepared from soybean hypocotyls. The spectrum, showing a peak at about 420 nm, remarkably resembles the absorption spectra of the Fe‐S centers of nonheme iron proteins. Disruption of the Fe‐S centers by treating SMP with mersalyl acid resulted in a substantial decrease in the efficiency of 1O2 generation, leaving an action spectrum whose pattern is significantly similar to the absorption spectrum of flavins, at least in the region of near UV and blue light wavelengths. Estimating the contribution of the Fe‐S centers to the generation of 1O2 from SMP, we suggest that the Fe‐S centers act as very important endogenous photosensitizers in plant cells, in so far as the type II mechanism is concerned. Possible involvement of mitochondrial flavoproteins in the generation of 1O2 is also discussed. Copyright © 1990, Wiley Blackwell. All rights reserved