Erythrosine B — a Specific Inhibitor of Plasmalemma ATPase in Intact Microalgae?

Abstract

Summary The effects of the fluorescein derivate erythrosine B, an inhibitor of isolated plasmalemma ATPases, on various physiological reactions of the microalage Dunalielle parva were tested, in order to prove its specificity under in vivo conditions. Although some effects of erythrosine B are in agreement with the supposed inhibition of plasmalemma ATPases and possible metabolic consequences of such an inhibition (acidification of the cytosol, inhibition of flagellar movement, reduction of growth, photosynthesis and dark C0 2 -fixation), the strong inhibition of isolated enzymes of the Calvin-cycle and of acid phosphatase, the interference of erythrosine B with photosynthetic electron transport, the occurrence of photodynamic effects and of photodecomposition call in severe questions about the specificity of this compound as an ATPase inhibitor during in vivo studies. It is concluded that in illuminated photosynthetic cells or tissues erythrosine B cannot be used as a specific inhibitor of plasmalemma ATPase. Even under dark conditions one must be extremely careful in the interpretation of inhibitory effects of erythrosine B as indications for the involvement of plasmalemma ATPases, since erythrosine B seems to react unspecifically with a variety of different enzymes after penetration of the cell.