<Li> E4P and a DHAP (formed from one of the G3P from the second CO fixation) are converted into sedoheptulose - 1, 7 - bisphosphate (7C) by aldolase enzyme . </Li> <Li> Sedoheptulose - 1, 7 - bisphosphatase (one of only three enzymes of the Calvin cycle that are unique to plants) cleaves sedoheptulose - 1, 7 - bisphosphate into sedoheptulose - 7 - phosphate, releasing an inorganic phosphate ion into solution . </Li> <Li> Fixation of a third CO generates two more G3P . The ketose S7P has two carbons removed by transketolase, giving ribose - 5 - phosphate (R5P), and the two carbons remaining on transketolase are transferred to one of the G3P, giving another Xu5P . This leaves one G3P as the product of fixation of 3 CO, with generation of three pentoses that can be converted to Ru5P . </Li> <Li> R5P is converted into ribulose - 5 - phosphate (Ru5P, RuP) by phosphopentose isomerase . Xu5P is converted into RuP by phosphopentose epimerase . </Li>

When is g3p removed from the calvin cycle