What is the name of the first stable compound formed in the Calvin cycle after CO2 fixation?

The first stable compound formed in the Calvin cycle after CO2 fixation is 3-phosphoglycerate, also called 3-PGA or PGA. It is a three-carbon molecule produced when the unstable product of carbon fixation splits.

The enzyme RuBisCO attaches carbon dioxide to ribulose-1,5-bisphosphate, or RuBP, which contains five carbon atoms. The resulting six-carbon intermediate is extremely unstable and breaks almost immediately into two molecules of 3-phosphoglycerate. Because that six-carbon compound is so short-lived, 3-phosphoglycerate is treated as the first stable product of the cycle.

3-Phosphoglycerate is not glucose or glyceraldehyde-3-phosphate. In the next stage, ATP and NADPH from the light-dependent reactions help convert 3-PGA into glyceraldehyde-3-phosphate, commonly abbreviated G3P. Some G3P can eventually contribute to sugars, while the rest helps regenerate RuBP so the cycle can continue. The cycle was mapped through experiments led by Melvin Calvin, Andrew Benson, and James Bassham.