Peptide alkaloids as inhibitors of photophosphorylation in spinach chloroplasts

Photophosphorylation in isolated spinach chloroplasts was inhibited by all 21 peptide alkaloids tested. Zizyphine A and B, adounetine Z, amphibine B, C and D and scutianine A inhibited the coupled but not the uncoupled electron transport. The other peptide alkaloids stimulated nonphosphorylating electron flow behaving like uncouplers. Aralionine A, lasiodine A and mucronine B were the strongest inhibitors and uncouplers. Lasiodine A and homaline stimulated by several times the light-induced proton uptake by chloroplasts.