Maple syrup urine disease (MSUD) is a rare autosomal recessive inherited disease associated with disruption of the normal activity of the branched-chain α-ketoacid dehydrogenase (BCKDH) complex, which is a multi-enzyme macromolecule with four catalytic components (E1α, E1β, E2 and E3) in humans. Here, PPM1K is linked to maple syrup urine disease.