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1,3-bisphosphoglycerate, often abbreviated as 1,3-BPG, is a vital intermediate compound in cellular respiration and photosynthesis. In the process of glycolysis, the breakdown of glucose, 1,3-bisphosphoglycerate is formed from glyceraldehyde-3-phosphate and inorganic phosphate. This reaction is catalyzed by the enzyme glyceraldehyde-3-phosphate dehydrogenase and is coupled with the reduction of NAD+ to NADH. The formation of 1,3-bisphosphoglycerate is a key energy-generating step in glycolysis because the phosphate group attached to the first carbon atom is a high-energy bond.

Subsequently, 1,3-bisphosphoglycerate is converted into 3-phosphoglycerate by the enzyme phosphoglycerate kinase. This reaction transfers a phosphate group from 1,3-bisphosphoglycerate to ADP, forming ATP. This is the first substrate-level phosphorylation event in glycolysis, meaning ATP is produced directly from a high-energy intermediate without the involvement of an electron transport chain.

In photosynthesis, 1,3-bisphosphoglycerate is also an important intermediate. It is produced during the Calvin cycle from 3-phosphoglycerate and ATP, and then it is reduced by NADPH to form glyceraldehyde-3-phosphate. This glyceraldehyde-3-phosphate can then be used to synthesize glucose or regenerate the starting molecule of the Calvin cycle, ribulose-1,5-bisphosphate. Therefore, 1,3-bisphosphoglycerate plays a central role in the energy metabolism of both heterotrophic and autotrophic organisms.