Studies on the O2 Evolution under Flash Light Illumination in Preparations of A nacystis nidulans

The 0 2 yield under flash light illumination in preparations o f Anacystis nidulans was examined in the presence o f redox components such as ferricyanide and ferrocyanide. When ferricyanide (1 mM) was added to the lyophilized, lysozyme treated and EDTA washed cells o f A. nidulans the familiar Joliot-Kok oscillalion with maximum on the third flash and periodicity o f four was observed (in the presence o f added CaCl2 and MnCl2). However, when the ferricyanide con­ centration was increased to about 8 mM, a reduction o f the 0 2 evolution under flash illumination was observed, and an 0 2 uptake could clearly be seen under the First and second flash. This 0 2 uptake was inhibited by DCM U and o-phenanthroline, but was not influenced by KCN or salicylhydroxamic acid. As ferrocyanide was progressively added to 1 mM ferricyanide, the oscillations faded out and the steady-state 0 2 evolution decreased. Light would progressively increase the 0 2 evolution and reduce the damping o f the oscillations. Two patterns o f 0 2 evolution under short saturating light flashes were observed with these Anacystis preparations on first illumination in the presence o f cations but in the absence o f ferri­ cyanide. One pattern corresponded to the typical pattern which has been repeatedly described in the literature, but the second pattern gave the indication o f an initial “over-reduced” state o f the photosystem II reaction center. With suitable procedures the two patterns were interchangeable. Moreover, the effect o f L-arginine on the flash pattern was exam ined. The results are discussed in connection with the possible dual function o f the previously described flavin protein as an L-amino acid oxidase and as a component o f the 0 2 evolving reaction center (E. K. Pistorius and H. Voss, Eur. J. Biochemistry 1 2 6 ,2 0 3 -2 0 9 (1982)).