Branched-chain alpha-keto acid dehydrogenase complex (BCKDC (also commonly referred to as BCKDH complex))

The Branched-chain alpha-keto acid dehydrogenase complex is a large mitochondrial multienzyme assembly responsible for catalyzing the irreversible oxidative decarboxylation step in the breakdown pathway for three essential branched-chain amino acids: leucine, isoleucine, and valine. The reaction products feed into energy metabolism pathways such as gluconeogenesis and lipogenesis. The enzyme consists primarily of three components: * E1 component*: A thiamin-dependent decarboxylase encoded by BCKDHA/BCKDHB, forming an α₂β₂ heterotetramer. * E2 component*: A lipoate-dependent dihydrolipoyl transacylase encoded by DBT, transferring acyl groups onto coenzyme A. * E3 component*: A FAD-dependent dihydrolipoyl dehydrogenase encoded by DLD, transferring electrons from reduced lipoamide onto NAD⁺. Activity is tightly regulated through reversible phosphorylation mediated by branched chain ketoacid dehydrogenase kinase (BCKDK)—which inhibits—and phosphatases like PP2Cm—which activate it. Dysfunction due to genetic mutations leads directly to maple syrup urine disease—a severe metabolic disorder characterized by accumulation of toxic metabolites with neurological consequences if untreated. Pharmacological modulation focuses on inhibiting BCKDK rather than directly targeting the core catalytic subunits; several small molecules including certain antihypertensives have been shown preclinically to enhance residual enzymatic function via this route.

Other names

Branched-chain alpha-ketoacid dehydrogenase complexBCKDH complexBranched-chain 2-oxo acid dehydrogenase complexBranched-chain ketoacid dehydrogenase complex

Drugs targeting this molecule typically act by inhibiting its negative regulator (BCKDK), leading to dephosphorylation and activation of the enzyme complex. This increases catabolism of branched-chain amino acids and reduces their plasma concentrations.