3-Phosphoglyceric acid (3PG, 3-PGA, or PGA) is the conjugate acid of 3-phosphoglycerate or glycerate 3-phosphate (GP or G3P). This glycerate is a

biochemically Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...

significant metabolic intermediate in both

glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...

and the Calvin-Benson cycle. The anion is often termed as PGA when referring to the Calvin-Benson cycle. In the Calvin-Benson cycle, 3-phosphoglycerate is typically the product of the spontaneous scission of an unstable 6-carbon intermediate formed upon CO₂ fixation. Thus, two equivalents of 3-phosphoglycerate are produced for each molecule of CO₂ that is fixed. In glycolysis, 3-phosphoglycerate is an intermediate following the dephosphorylation ( reduction) of

1,3-bisphosphoglycerate 1,3-Bisphosphoglyceric acid (1,3-Bisphosphoglycerate or 1,3BPG) is a 3-carbon organic molecule present in most, if not all, living organisms. It primarily exists as a metabolic intermediate in both glycolysis during respiration and the Calvin cycl ...

Glycolysis

In the glycolytic pathway, 1,3-bisphosphoglycerate is dephosphorylated to form 3-phosphoglyceric acid in a coupled reaction producing two

ATP ATP may refer to: Companies and organizations * Association of Tennis Professionals, men's professional tennis governing body * American Technical Publishers, employee-owned publishing company * ', a Danish pension * Armenia Tree Project, non ...

via

substrate-level phosphorylation Substrate-level phosphorylation is a metabolism reaction that results in the production of ATP or GTP by the transfer of a phosphate group from a substrate directly to ADP or GDP. Transferring from a higher energy (whether phosphate group atta ...

. The single phosphate group left on the 3-PGA molecule then moves from an end carbon to a central carbon, producing 2-phosphoglycerate. This phosphate group relocation is catalyzed by phosphoglycerate mutase, an enzyme that also catalyzes the reverse reaction.

Calvin-Benson cycle

In the light-independent reactions (also known as the Calvin-Benson cycle), two 3-phosphoglycerate molecules are synthesized. RuBP, a 5-carbon sugar, undergoes

carbon fixation Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as ...

, catalyzed by the rubisco enzyme, to become an unstable 6-carbon intermediate. This intermediate is then cleaved into two, separate 3-carbon molecules of 3-PGA. One of the resultant 3-PGA molecules continues through the Calvin-Benson cycle to be regenerated into RuBP while the other is reduced to form one molecule of glyceraldehyde 3-phosphate (G3P) in two steps: the

phosphorylation In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, wh ...

of 3-PGA into

1,3-bisphosphoglyceric acid 1,3-Bisphosphoglyceric acid (1,3-Bisphosphoglycerate or 1,3BPG) is a 3-carbon organic molecule present in most, if not all, living organisms. It primarily exists as a metabolic intermediate in both glycolysis during respiration and the Calvin cycl ...

via the enzyme phosphoglycerate kinase (the reverse of the reaction seen in glycolysis) and the subsequent catalysis by

glyceraldehyde 3-phosphate dehydrogenase Glyceraldehyde 3-phosphate dehydrogenase (abbreviated GAPDH) () is an enzyme of about 37kDa that catalyzes the sixth step of glycolysis and thus serves to break down glucose for energy and carbon molecules. In addition to this long establishe ...

into G3P. G3P eventually reacts to form the sugars such as glucose or

fructose Fructose, or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galacto ...

or more complex

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...

es.

Amino acid synthesis

Glycerate 3-phosphate (formed from 3-phosphoglycerate) is also a precursor for

serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − form un ...

, which, in turn, can create

cysteine Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. When present as a deprotonated catalytic residue, sometime ...

and glycine through the homocysteine cycle.

Measurement

3-phosphoglycerate can be separated and measured using paper chromatography as well as with column chromatography and other chromatographic separation methods. It can be identified using both

gas-chromatography Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, ...

and liquid-chromatography mass spectrometry and has been optimized for evaluation using tandem MS techniques.

References

{{DEFAULTSORT:Phosphoglyceric Acid, 3- Carboxylate anions Organophosphates Photosynthesis Glycolysis

Glycolysis

Calvin-Benson cycle

Amino acid synthesis

Measurement

See also

References