In support of these findings, individuals with maple syrup urine disease (MSUD), a rare genetic disorder that causes a mutation in genes encoding branched-chain α keto-acid dehydrogenase (BCKDH) complex, the rate-limiting enzyme in BCAA degradation pathway, have nearly 10-fold higher BCAAs and their toxic keto-acids in plasma compared to healthy controls [20,21], leading to serious neurological impairments. The gene discussed is PPM1K; the disease is maple syrup urine disease.