Synthalin: An inhibitor of energy transfer in chloroplasts

Abstract

Synthalin, decamethylene diguanidine, has been found to act as an energy-transfer inhibitor in chloroplasts. Both ATP formation and the accompanying coupled electron flow were inhibited in a parallel manner, but neither the basal rate of electron flow (minus phosphate) nor that observed in the presence of uncouplers such as CCCP or NH 4Cl were significantly affected. Electron flow stimulated by arsenate was inhibited to the same extent as that stimulated by phosphate. Light-induced proton uptake was not affected at synthalin concentrations which completely inhibited ATP formation. PMS mediated phosphorylation was less sensitive to synthalin than phosphorylation mediated by ferricyanide or methyl viologen since 10 −3 m synthalin was required for 50% inhibition with PMS whereas only 2 × 10 −4 m was required for 50% inhibition with the other electron transport agents.