is a coenzyme A
derivative of propionic acid
Metabolism in animals
There are several different ways in which it is formed:
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 by methylmalonyl-CoA mutase, an enzyme requiring cobalamin to catalyze the carbon-carbon bond migration.
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.
- Halarnkar P, Blomquist G (1989). "Comparative aspects of propionate metabolism". Comp. Biochem. Physiol., B 92 (2): 227–31.