Branched-chain alpha-ketoacid dehydrogenase complex E2 subunit (DBT)

The Branched-chain alpha-ketoacid dehydrogenase complex E2 subunit (DBT) is a core structural and catalytic component of the mitochondrial BCKDH multienzyme complex (UniProt P11182). It functions as a dihydrolipoyl transacylase, facilitating the transfer of acyl groups to coenzyme A during the catabolism of branched-chain amino acids (BCAAs) such as leucine, isoleucine, and valine (NCBI Gene ID 1629). Mutations in the DBT gene are the primary cause of Maple Syrup Urine Disease (MSUD) Type II, a metabolic disorder characterized by the accumulation of toxic BCAAs and their alpha-keto acid derivatives, leading to severe neurological impairment and metabolic acidosis (StatPearls NBK532977). While the E2 subunit itself is not a direct binder for most conventional small molecules, it is the functional target of therapies like sodium phenylbutyrate, which indirectly enhances complex activity by inhibiting the regulatory kinase BCKDK (PubMed 21310445). Additionally, experimental compounds like BT2 are being investigated for their ability to allosterically inhibit BCKDK, thereby restoring the flux through the E2-containing complex in patients with residual enzyme activity (PubMed 23512315). This target is central to managing metabolic homeostasis and preventing the neurocognitive deficits associated with BCAA dysregulation.

Other names

Dihydrolipoyl transacylaseBCKDH-E2E2 component of BCKAD complexDihydrolipoyllysine-residue acetyltransferase component of branched-chain alpha-ketoacid dehydrogenase complexDihydrolipoamide acetyltransferase component of branched-chain alpha-ketoacid dehydrogenase complex

Indirect activation of the BCKDH complex through the inhibition of branched-chain alpha-ketoacid dehydrogenase kinase (BCKDK), which reduces the inhibitory phosphorylation of the E1 subunit, thereby increasing the overall catalytic throughput of the E2-containing complex (PubMed 21310445).