Glyceraldehyde 3-phosphate


Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is the metabolite that occurs as an intermediate in several central pathways of all organisms. With the chemical formula HCCHCH2OPO32-, this anion is a monophosphate ester of glyceraldehyde.

An intermediate in both glycolysis and gluconeogenesis

Formation

D-glyceraldehyde 3-phosphate is formed from the following three compounds in reversible reactions:

The numbering of the carbon atoms indicates the fate of the carbons according to their position in fructose 6-phosphate.

D-glyceraldehyde 3-phosphate is also of some importance since this is how glycerol enters the glycolytic and gluconeogenic pathways. Furthermore, it is a participant in and a product of the pentose phosphate pathway.

Interactive pathway map

An intermediate in photosynthesis

During plant photosynthesis, 2 equivalents of glycerate 3-phosphate are produced by the first step of the light-independent reactions when ribulose 1,5-bisphosphate and carbon dioxide are catalysed by the rubisco enzyme. The GP is converted to D-glyceraldehyde 3-phosphate using the energy in ATP and the reducing power of NADPH as part of the Calvin cycle. This returns ADP, phosphate ions Pi, and NADP+ to the light-dependent reactions of photosynthesis for their continued function.
RuBP is regenerated for the Calvin cycle to continue.
G3P is generally considered the prime end-product of photosynthesis and it can be used as an immediate food nutrient, combined and rearranged to form monosaccharide sugars, such as glucose, which can be transported to other cells, or packaged for storage as insoluble polysaccharides such as starch.

Balance sheet

6 CO2 + 6 RuBP →12 G3P
10 G3P → 6 RuBP
2 G3P → glucose.

In tryptophan biosynthesis

Glyceraldehyde 3-phosphate occurs as a byproduct in the biosynthesis pathway of tryptophan, an essential amino acid that cannot be produced by the human body.

In thiamine biosynthesis

Glyceraldehyde 3-phosphate occurs as a reactant in the biosynthesis pathway of thiamine, another substance that cannot be produced by the human body