Photosynthesis by isolated chloroplasts.

TLDR: Evidence is given for the action of the photochemically generated assimilatory power on two phases of the reductive carbohydrate cycle in isolated chloroplasts: the carboxylative phase which includes the phosphorylation of ribulose monophosphate and the fixation of COZ, and the reduction of 3-phosphoglyceric acid and the formation of hexose phosphate.

Abstract: A previous article (1) has described a reconstituted “catalytic” chloroplast system in which, as in the intact leaf, the dark reactions of photosynthetic COz assimilation depended on light for the generation of assimilatory power (2), i.e. reduced triphosphopyridine nucleotide and adenosine triphosphate. The companion paper (3) discusses the sitesof action of photochemically generated ATP and TPNHz in the reductive carbohydrate cycle which operates in isolated chloroplasts. This communication gives further evidence for the action of the photochemically generated assimilatory power on two phases of the reductive carbohydrate cycle in isolated chloroplasts: the carboxylative phase which includes the phosphorylation of ribulose monophosphate and the fixation of COZ, and the reductive phase, which includes the reduction of 3-phosphoglyceric acid and the formation of hexose phosphate. The evidence to be presented here is derived from experiments in which the availability of ATP and TPNHz for CO2 assimilation was decreased either by the use of inhibitors or by special arrangements of experimental conditions; certain of the inhibitors acted on single enzymatic reactions in CO2 assimilation.