Inhibitor Studies on Light-Induced Phosphorylation in Isolated Spinach Chloroplasts.

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Abstract
Light-induced phosphorylation in isolated chloroplasts is greatly stimulated by the addition of several types of compounds capable of undergoing reduction and oxidation, among them flavin nucleotides. Whether the stimulatory agent is a flavin or not, 4 x 10-5 [image] atebrin completely or almost completely inhibits the phosphorylation, indicating that endogenous chloroplast flavin is an obligatory participant in this system. The inhibition is not reversed by high concentrations of flavin nucleotide. In fact, flavin adenine dinucleotide (2 x 10-3 [image]) gives nearly complete and flavin mononucleotide (5 x 10-3 [image]) partial inhibition of phosphate esterification. Amytal gives only slight inhibition. Low concentrations of antimycin A, 2-n-heptyl-4-hydroxyquinoline-N-oxide and oligomycin A have no inhibitory effect on light-induced phosphorylation in isolated spinach chloroplasts comparable to the effects on light-induced phosphorylation in a bacterial. (Rhodospirillum rubrum) extract and respiration and phosphorylation in animal mitochondria. The hypothesis that added compounds effective as cofactors, such as FMN, menadione and phenazine methosulfate, may bridge over a gap in electron transport of the chloroplasts as they are presently isolated, is discussed.