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
In biochemistry, a metabolite is an intermediate or end product of metabolism.
The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...
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 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-phosphate ( ...
.
''The numbering of the carbon atoms indicates the fate of the carbons according to their position in fructose 6-phosphate.''
*Dihydroxyacetone phosphate (
DHAP
Dhap is a market center in Api Municipality in Darchula District in the Mahakali Zone of western Nepal. The formerly Village Development Committee was merged to form new municipality since 18 May 2014. At the time of the 1991 Nepal census it h ...
), 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), catalyzed 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 ...
.
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 cycl ...
in
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) ...
.
D-glyceraldehyde 3-phosphate is also of some importance since this is how
glycerol (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, 2 equivalents of
glycerate 3-phosphate (GP; also known as 3-phosphoglycerate) are produced by the first step of the
light-independent reactions 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 are catalysed by the
rubisco enzyme. The GP is converted to D-glyceraldehyde 3-phosphate (G3P) using the energy in
ATP and the reducing power of
NADPH
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 NAD ...
as part of the
Calvin cycle
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 ...
. This returns
ADP
Adp or ADP may refer to:
Aviation
* Aéroports de Paris, airport authority for the Parisian region in France
* Aeropuertos del Perú, airport operator for airports in northern Peru
* SLAF Anuradhapura, an airport in Sri Lanka
* Ampara Airp ...
, 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 NAD ...
+ 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, 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 (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 am ...
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