Dehydrogenation occurs between the alpha and beta carbons (C2 and C3) in a FAD-linked reaction catalyzed by acyl CoA dehydrogenase. The oxidation power of FAD is required to oxidize the alkyl chain, much as it is in the succinate dehydrogenase reaction of the tricarboxylic acid cycle. The product contains a trans- double bond. Involvement of the beta-carbon in this and subsequent steps gives the pathway its name.
There are three fatty acyl CoA dehydrogenases. Each is specific for a different acyl chain length, so different enzymes are involved in different stages of beta-oxidation.
MCAD deficiency is thought to be one of the most common inborn errors of metabolism.