Glycerol 3-phosphate
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Biosynthesis
Glycerol 3-phosphate is synthesized by reducing dihydroxyacetone phosphate (DHAP), an intermediate in glycolysis. The reduction is catalyzed by glycerol-3-phosphate dehydrogenase. DHAP and thus glycerol 3-phosphate can also be synthesized from amino acids and citric acid cycle intermediates via the glyceroneogenesis pathway.
It is also synthesized by the phosphorylation of glycerol, which is generated by hydrolysis of fats. This esterification is catalyzed by glycerol kinase.
Metabolism and biological function
Glycerol 3-phosphate is a starting material for de novo synthesis of glycerolipids. In eukaryotes, it is first acylated on its sn-1 position by an ER- or mitochondrial membrane enzyme, glycerol-3-phosphate O-acyltransferase. A second acyl group is subsequently installed on the sn-2 position making phosphatidic acids.
- G1P + Acyl-CoA → Lysophosphatidic acid + CoA
Glycerol-1-phosphatase catalyzes the hydrolysis of glycerol 3-phosphate to regenerate glycerol, allowing glycerol fermentation to produce glycerol from glucose through glycolysis pathway. A number of organisms express this enzyme.[1]
Shuttle system
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Glycerol-3-phosphate dehydrogenases are located both in the cytosol and the intermembrane face of mitochondrial inner membrane. Glycerol 3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP) are molecules so small that they can permeate the mitochondrial outer membrane through porins and shuttle between two dehydrogenases. Using this shuttle system, NADH generated by cytosolic metabolisms including glycolysis is reoxidized to NAD+ reducing DHAP to G3P, and the reducing equivalent can be used for generating a proton gradient across the mitochondrial inner membrane by coupling and oxidizing G3P and reducing quinone.
The Glycerol 3-phosphate shuttle is an emergency back-up system to supply neurons' demand of energy.[2]
Dephosphorylation
Script error: No such module "Labelled list hatnote". Glycerol-3-phosphate was found to be a substrate for the enzyme phosphoglycolate phosphatase (PGP, or G3PP) in mammals in 2015.[1] G3PP activity has subsequently been suggested to have a regulatory role in central metabolism[1] and stress response.[3]
Glycerol 1-phosphate
Glycerol 1-phosphate, sometimes called as DScript error: No such module "Check for unknown parameters".-glycerol 3-phosphate, is the enantiomer of glycerol 3-phosphate. Eukaryotes use the 3-phosphate, or LScript error: No such module "Check for unknown parameters".-configuration, for glycerolipid backbone. The 1-phosphate is specifically found in archaeal lipids.[4]
Notes
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