Enzyme defects indicated by solid bars are numbered as follows: (1), branched-chain 2-ketoacid dehydrogenase complex deficiency (MSUD, maple syrup urine disease); (2), isovaleryl-CoA dehydrogenase deficiency (isovaleric acidemia); (3), isolated 3-methylcrotonyl-CoA carboxylase deficiency; (4), 3-methylcrotonyl-CoA carboxylase deficiency as part of a multiple carboxylase deficiency due to nutritional biotin deficiency or biotinidase deficiency or holocarboxylase synthetase deficiency or carbonic anhydrase VA deficiency or MT-ATP6 deficiency; (5),
3-methylglutaconyl-CoA hydratase deficiency; (6), 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase deficiency.