The catalysis by modified chloroplasts of the P i ↔ ATP, P i ↔ HOH and ATP ↔ HOH exchange reactions in the absence of light

Abstract

P i ↔ HOH, ATP ↔ HOH and P i ↔ ATP exchanges, probably reflecting the phosphorylation and water formation reactions of photosynthetic phosphorylation are catalyzed in the dark by lettuce chloroplasts after exposure to light and dithiothreitol. A marked stimulation of the P i ↔ HOH exchange by ATP and of the ATP ↔ and of the ATP ↔ HOH exchange by P i, and a lack of ADP inhibition of the P i ↔ ATP and ATP ↔ HOH exchanges are consistent with all exchanges occurring by dynamic reversal of ATP cleavage at the catalytic site.