Function 
Acyl-CoA dehydrogenase (ACDH) catalyzes the introduction of a double bond between C2 and C3 of the thio-ester CoA substrate.  This is the first reaction in fatty acid metabolism which produces acetyl-CoA.  FAD is the cofactor of ACDH activity.  ACDH is classified according to the length of its substrates as short- (SCAD), medium- (MCAD), very- and very long-chain (VLCAD) ACDH.  MCAD can bind a broad range of chain length acyl-CoA substrates.[1] See also Beta oxidation and Glutaryl-CoA dehydrogenase.
- Glutaryl-CoA dehydrogenase is required for the metabolism of Lys, Trp and hydroxyLys.
 - Isovaleryl-CoA dehydrogenase catalyzes the conversion of isovaleryl-CoA to 3-methylcrotonyl-CoA[2].
 - 3-hydroxyacyl-CoA dehydrogenase oxidates straight chain 3-hydroxyacyl-CoA[3].
 
  Disease 
Impairment of the activity of ACDH causes a variety of diseases associated with lack of fatty acid metabolism.  MCAD mutations are associated with Sudden Infant Death and with Medium-chain Acyl-CoA Dehydrogenase Deficiency (MCADD)[4]. For details see Investigating the Mechanisms of Active Site Mutations to the 1T9G WT MCAD Protein to Better Understand Medium Chain Acyl-CoA Dehydrogenase Deficiency (MCADD). SCAD deficiency is a recessive disorder of fatty acid β-oxidation.
  Structural highlights 
SCAD is a homodimer with a single FAD binding site.  with 4 FAD binding sites in the subunits interface and 4 binding sites for acyl-CoA substrate within each monomer. 
- One of the  in homotetramer of rat ACDH. Water molecules are shown as red spheres.
 - One of the  in homotetramer of rat ACDH.[5] 
 
 3D structures of acyl-CoA dehydrogenase
Acyl-CoA dehydrogenase 3D structures