Isovaleryl-CoA dehydrogenase (IVD) is an is an acyl-CoA dehydrogenase, which catalyzes the third step in leucine catabolism, the conversion of isovaleryl-CoA (3-methylbutyryl-CoA) into 3-methylcrotonyl-CoA. IVD is a homotetramer and has the greatest affinity for small branched chain substrates.