Cofactors and Chemistry

Lipoic Acid

Chemical structure lipoic acid and lysyl-lipoamide.
In its oxidized (top left) and reduced (top right) states.
It is always covalently attached to an enzyme via an amide bond to a Lysine.		 3D structure of reduced lipoic acid. It is shown covalently linked to the enzymes Lysine (to the left side of the structure)

Vitamin Dependence: Technically, lipoic Acid does not qualify as a vitamin as it is not a required part of our diet. You can read more about Lipoic acid synthesis and deficiencies here.

Lipoic acid is involved in enzymes that catalyze the oxidative decarboxylation of an α-keto acid. Its function is to provide "transport" from the decarboxylation active site to the "oxidation" active site within the enzyme. It is used mostly in conjunction with Thiamine Pyrophosphate as shown below.
SOME ENZYMES USING THIS COFACTOR
pyruvate dehydrogenase Key enzyme adapter between glycolysis and the Krebs cycle. We will learn more about this enzyme in module 6.
α-ketoglutatrate dehydrogenase this enzyme is part of the Krebs cycle. We will learn more about it in Module 7.