Thiol-disulfide oxidoreductase involved in the redox regulation of enzymes of both reductive pentose phosphate pathway (Calvin-Benson cycle) and oxidative pentose phosphate pathway. Under light or reducing conditions, activates in chloroplast the glyceraldehyde-3-phosphate dehydrogenase, the phosphoribulokinase and the fructose-1,6-bisphosphate phosphatase, and inhibits the glucose-6-phosphate dehydrogenase. Glutathionylation at Cys-126 decreases its ability to be reduced by ferredoxin-thioredoxin reductase and reduces its efficiency in activating target chloroplastic enzymes. Belongs to the thioredoxin family. Plant F-type subfamily.