Propionyl-CoA
| Propionyl-CoA | |
|---|---|
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| IUPAC name S-[2-[3-[[4-[[[(2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-4-hydroxy-3-phosphonooxyoxolan-2-yl]methoxy-hydroxyphosphoryl]oxy-hydroxyphosphoryl]oxy-2-hydroxy-3,3-dimethylbutanoyl]amino]propanoylamino]ethyl] propanethioate | |
| Other names Propionyl Coenzyme A; Propanoyl Coenzyme A | |
| Identifiers | |
| CAS number | 317-66-8  |
| PubChem | 439164 |
| ChemSpider | 21106467  |
| MeSH | propionyl-coenzyme+A |
| Jmol-3D images | {{#if:CCC(=O)SCCNC(=O)CCNC(=O)C(O)C(C)(C)COP(O)(=O)OP(O)(=O)OCC3OC(n2cnc1c(N)ncnc12)[C@H](O)[C@@H]3OP(O)(O)=O|Image 1 |
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| Properties | |
| Molecular formula | C24H40N7O17P3S |
| Molar mass | 823.60 g/mol |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa) | |
| Infobox references | |
Propionyl-CoA is a coenzyme A derivative of propionic acid.
Metabolism in animals
Production
There are several different ways in which it is formed:
- It is formed as a product of beta-oxidation of odd-chain fatty acids.
- It is also a product of metabolism of isoleucine and valine.
- It is a product of alpha-ketobutyric acid, which in turn is a product of digestion of threonine and methionine.
Metabolic fate
In mammals, propionyl-CoA is converted to (S)-methylmalonyl-CoA by propionyl-CoA carboxylase, a biotin-dependent enzyme also requiring bicarbonate and ATP.
This product is converted to (R)-methylmalonyl-CoA by methylmalonyl-CoA racemase.
(R)-Methylmalonyl-CoA is converted to succinyl-CoA, an intermediate in the tricarboxylic acid cycle, by methylmalonyl-CoA mutase, an enzyme requiring cobalamin to catalyze the carbon-carbon bond migration.
The methylmalonyl-CoA mutase mechanism begins with the cleavage of the bond between the 5' CH2- of 5'-deoxyadenosyl and the cobalt, which is in its 3+ oxidation state (III), which produces a 5'-deoxyadenosyl radical and cabalamin in the reduced Co(II) oxidation state.
Next, this radical abstracts a hydrogen atom from the methyl group of methylmalonyl-CoA, which generates a methylmalonyl-CoA radical. It is believed that this radical forms a carbon-cobalt bond to the coenzyme, which is then followed by the rearrangement of the substrate's carbon skeleton, thus producing a succinyl-CoA radical. This radical then goes on to abstract a hydrogen from the previously produced 5'-deoxyadenosine, again creating a deoxyadenosyl radical, which attacks the coenzyme to reform the initial complex.
A defect in methylmalonyl-CoA mutase enzyme results in methylmalonic aciduria, a dangerous disorder that causes a lowering of blood pH.
Metabolism in plants and insects
In plants and insects propionyl-CoA is metabolized to acetate in a very different way, similar to beta-oxidation.
Not all details of this pathway have been worked out, but it appears to involve formation of acrylyl-CoA, then 3-hydroxypropionyl-CoA.
This is metabolized with loss of carbon 1 of 3-hydroxypropionyl-CoA as carbon dioxide, while carbon 3 becomes carbon 1 of acetate.
References
- Halarnkar P, Blomquist G (1989). "Comparative aspects of propionate metabolism". Comp. Biochem. Physiol., B 92 (2): 227–31. doi:10.1016/0305-0491(89)90270-8. PMID 2647392.
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