IVD is a mitochondrial matrix enzyme that is part of the cyl-CoA dehydrogenase family which catalyzes the third step in leucine catabolism. The genetic deficiency of IVD leads to a buildup of isovaleric acid, which is toxic to the central nervous system and results in isovaleric acidemia. IVD is a homotetrameric flavoenzyme which catalyzes the conversion of isovaleryl-CoA to 3-methylcrotonyl-CoA.