Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is a
metabolite that occurs as an intermediate in several central
pathways of all organisms.
[Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. .] With the
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbol ...
H(O)CCH(OH)CH
2OPO
32-, this anion is a
monophosphate ester of
glyceraldehyde
Glyceraldehyde (glyceral) is a triose monosaccharide with chemical formula C3 H6 O3. It is the simplest of all common aldoses. It is a sweet, colorless, crystalline solid that is an intermediate compound in carbohydrate metabolism. The word comes ...
.
An intermediate in both glycolysis and gluconeogenesis
Formation
D-glyceraldehyde 3-phosphate is formed from the following three compounds in reversible reactions:
*Fructose-1,6-bisphosphate (
F1,6BP), catalyzed by
aldolase
Fructose-bisphosphate aldolase (), often just aldolase, is an enzyme catalyzing a reversible reaction that splits the aldol, fructose 1,6-bisphosphate, into the triose phosphates dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phospha ...
.
''The numbering of the carbon atoms indicates the fate of the carbons according to their position in fructose 6-phosphate.''
*Dihydroxyacetone phosphate (
DHAP), catalyzed by
triose phosphate isomerase
Triose-phosphate isomerase (TPI or TIM) is an enzyme () that catalyzes the reversible interconversion of the triose phosphate isomers dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate.
TPI plays an important role in glycolysis and ...
.
*1,3-bisphosphoglycerate (
1,3BPG
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 ...
), catalyzed by
glyceraldehyde 3-phosphate dehydrogenase.
As a substrate
*To produce
1,3-bisphospho-D-glycerate
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 cyc ...
in
glycolysis.
D-glyceraldehyde 3-phosphate is also of some importance since this is how
glycerol
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
(as DHAP) enters the glycolytic and gluconeogenic pathways. Furthermore, it is a participant in and a product of the
pentose phosphate pathway
The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt and the HMP Shunt) is a metabolic pathway parallel to glycolysis. It generates NADPH and pentoses (5-carbon sugars) as well as ribose 5-pho ...
.
Interactive pathway map
,
An intermediate in photosynthesis
During plant
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
, 2 equivalents of
glycerate 3-phosphate
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 significant metabolic intermediate in both glycolysis and the Calvin-Benson cycle. The ...
(GP; also known as 3-phosphoglycerate) are produced by the first step of the
light-independent reaction
The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...
s when
ribulose 1,5-bisphosphate
Ribulose 1,5-bisphosphate (RuBP) is an organic substance that is involved in photosynthesis, notably as the principal acceptor in plants. It is a colourless anion, a double phosphate ester of the ketopentose (ketone-containing sugar with five ca ...
(RuBP) and
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
are catalysed by the
rubisco
Ribulose-1,5-bisphosphate carboxylase-oxygenase, commonly known by the abbreviations RuBisCo, rubisco, RuBPCase, or RuBPco, is an enzyme () involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is con ...
enzyme. The GP is converted to D-glyceraldehyde 3-phosphate (G3P) 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
Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require N ...
+ to the
light-dependent reaction
Light-dependent reactions is jargon for certain photochemical reactions that are involved in photosynthesis, the main process by which plants acquire energy. There are two light dependent reactions, the first occurs at photosystem II (PSII) and ...
s 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
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
, which can be transported to other cells, or packaged for storage as insoluble
polysaccharides such as
starch.
Balance sheet
6 CO
2 + 6 RuBP (+ energy from 12
ATP and 12 NADPH) →12 G3P (3-carbon)
10 G3P (+ energy from 6
ATP) → 6 RuBP (i.e. starting material regenerated)
2 G3P →
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
(6-carbon).
In tryptophan biosynthesis
Glyceraldehyde 3-phosphate occurs as a byproduct in the biosynthesis pathway of
tryptophan
Tryptophan (symbol Trp or W)
is an α-amino acid that is used in the biosynthesis of proteins. Tryptophan contains an α-amino group, an α-carboxylic acid group, and a side chain indole, making it a polar molecule with a non-polar aromatic ...
, an essential
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
that cannot be produced by the human body.
In thiamine biosynthesis
Glyceraldehyde 3-phosphate occurs as a reactant in the biosynthesis pathway of
thiamine
Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient, that cannot be made in the body. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thi ...
(Vitamin B
1), another substance that cannot be produced by the human body.
References
External links
D-Glyceraldehyde 3-phosphate and the reactions and pathways it participates in from the
KEGG PATHWAY Database
Glyceraldehyde 3-phosphate and the reactions and pathways it participates in from the KEGG PATHWAY Database
{{Fructose and galactose metabolic intermediates
Photosynthesis
Organophosphates
Phosphate esters
Glycolysis