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Protein phosphatase 2Cm is a critical regulator of branched-chain amino acid catabolism in mice and cultured cells.


The branched-chain amino acids (BCAA) are essential amino acids required for protein homeostasis, energy balance, and nutrient signaling. In individuals with deficiencies in BCAA, these amino acids can be preserved through inhibition of the branched-chain-alpha-ketoacid dehydrogenase (BCKD) complex, the rate-limiting step in their metabolism. BCKD is inhibited by phosphorylation of its E1alpha subunit at Ser293, which is catalyzed by BCKD kinase. During BCAA excess, phosphorylated Ser293 (pSer293) becomes dephosphorylated through the concerted inhibition of BCKD kinase and the activity of an unknown intramitochondrial phosphatase. Using unbiased, proteomic approaches, we have found that a mitochondrial-targeted phosphatase, PP2Cm, specifically binds the BCKD complex and induces dephosphorylation of Ser293 in the presence of BCKD substrates. Loss of PP2Cm completely abolished substrate-induced E1alpha dephosphorylation both in vitro and in vivo. PP2Cm-deficient mice exhibited BCAA catabolic defects and a metabolic phenotype similar to the intermittent or intermediate types of human maple syrup urine disease (MSUD), a hereditary disorder caused by defects in BCKD activity. These results indicate that PP2Cm is the endogenous BCKD phosphatase required for nutrient-mediated regulation of BCKD activity and suggest that defects in PP2Cm may be responsible for a subset of human MSUD.

Pubmed ID: 19411760


  • Lu G
  • Sun H
  • She P
  • Youn JY
  • Warburton S
  • Ping P
  • Vondriska TM
  • Cai H
  • Lynch CJ
  • Wang Y


The Journal of clinical investigation

Publication Data

June 5, 2009

Associated Grants

  • Agency: NIDDK NIH HHS, Id: DK053843
  • Agency: NIDDK NIH HHS, Id: DK062880
  • Agency: NHLBI NIH HHS, Id: HL080111
  • Agency: NHLBI NIH HHS, Id: HL087132
  • Agency: NHLBI NIH HHS, Id: HL62311
  • Agency: NHLBI NIH HHS, Id: HL70079
  • Agency: PHS HHS, Id: HLP01-008111
  • Agency: NIDDK NIH HHS, Id: R01 DK062880
  • Agency: NIDDK NIH HHS, Id: R01 DK062880-06
  • Agency: NIDDK NIH HHS, Id: R01 DK062880-07
  • Agency: NHLBI NIH HHS, Id: R01 HL087132
  • Agency: NHLBI NIH HHS, Id: R21 HL096041
  • Agency: NCRR NIH HHS, Id: RR 022371
  • Agency: NCRR NIH HHS, Id: S10 RR022371

Mesh Terms

  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
  • Amino Acids, Branched-Chain
  • Animals
  • Cells, Cultured
  • Cercopithecus aethiops
  • Humans
  • Mice
  • Mice, Knockout
  • Models, Animal
  • Phosphoprotein Phosphatases
  • Phosphorylation
  • Protein Binding
  • Protein Subunits
  • Reactive Oxygen Species
  • Substrate Specificity