Calvin cycle
The Calvin cycle is a carbon fixation pathway; it is part of photosynthesis, which convert carbon dioxide and other compounds into glucose. It and gluconeogenesis share a series of four reversible reactions. In both pathways 3-phosphoglycerate (3-PGA or 3-PG) is reduced to fructose 1,6-bisphosphate with aldolase catalyzing the last reaction. A fifth reaction, catalyzed in both pathways by fructose 1,6-bisphosphatase, hydrolyzes the fructose 1-6-bisphosphate to fructose 6-phosphate and inorganic phosphate. The large decrease in free energy makes this reaction irreversible. In the Calvin cycle aldolase also catalyzes the production of sedoheptulose 1,7-bisphosphate from DHAP and erythrose 4-phosphate. The chief products of the Calvin cycle are triose phosphate (TP), which is a mixture of DHAP and G3P, and fructose 6-phosphate. Both are also needed to regenerate RuBP. The aldolase used by plants and algae in the Calvin cycle is usually a plastid-targeted protein encoded by a nuclear gene.