Synergetic inhibition of photophosphorylation and uncoupled electron transport by N, N′-dicyclohexylcarbodiimide and alcohols in pea chloroplasts

Abstract

It is shown that the inhibitory effect of N, N′-dicyclohexylcarbodiimide (DCCD) on photophosphorylation and uncoupled electron transfer from H 2O to methylviologen (MV) in pea chloroplasts depends upon solvent concentration. Being applied as a solution in dimethyl sulfoxide (DMSO) DCCD did not suppress uncoupled electron transfer and inhibited photophosphorylation independently from DMSO concentration. If DCCD was applied as methanolic or ethanolic solution its concentration sufficient for half-maximum inhibition [I] 50 of both photophosphorylation and uncoupled electron transfer decreased at increasing alcohol content. The data suggest that the synergistic effect of DCCD and alcohols is connected with DCCD-catalyzed etherification of some carboxylic groups which are important for chloroplast electron transfer.