Abstract The O2 yield under flash light illumination in preparations of Anacystis nidulans was examined in the presence of redox components such as ferricyanide and ferrocyanide. When ferricyanide (1 mᴍ) was added to the lyophilized, lysozyme treated and EDTA washed cells of A. nidulans the familiar Joliot-Kok oscillalion with maximum on the third flash and periodicity of four was observed (in the presence of added CaCl2 and MnCl2). However, when the ferricyanide concentration was increased to about 8 mᴍ , a reduction of the O2 evolution under flash illumination was observed, and an O2 uptake could clearly be seen under the first and second flash. This O2 uptake was inhibited by DCMU and o-phenanthroline, but was not influenced by KCN or salicylhydroxamic acid. As ferrocyanide was progressively added to 1 mᴍ ferricyanide, the oscillations faded out and the steady-state O2 evolution decreased. Light would progressively increase the O2 evolution and reduce the damping of the oscillations. Two patterns of O2 evolution under short saturating light flashes were observed with these Anacystis preparations on first illumination in the presence of cations but in the absence of ferricyanide. One pattern corresponded to the typical pattern which has been repeatedly described in the literature, but the second pattern gave the indication of an initial “over-reduced” state of the photosystem II reaction center. With suitable procedures the two patterns were interchangeable. Moreover, the effect of ʟ-arginine on the flash pattern was examined. The results are discussed in connection with the possible dual function of the previously described flavin protein as an ʟ-amino acid oxidase and as a component of the O2 evolving reaction center (E. K. Pistorius and H. Voss, Eur. J. Biochemistry 126,203-209 (1982)).
Effect of Mn2+
and Ca2+
on O2
evolution and on the variable fluorescence yield associated with Photosystem II in preparations of Anacystis nidulans
