| Gene name | UniProt ID | Protein name | Organism | EC number | Molecular weight | Structure | Cofactors | Substrates | Products | Subcellular localization | Key domains | Disease association | Regulatory mechanism |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| **BCKDHB** | **P21953** | Branched-chain alpha-keto acid dehydrogenase E1 component beta chain; 2-oxoisovalerate dehydrogenase subunit beta, mitochondrial | *Homo sapiens* | **EC 1.2.4.4** | E1β subunit ~37.8 kDa; E1 complex contains two 37.8 kDa β subunits plus two 45.5 kDa α subunits (pqac-00000003) | **α2β2 heterotetramer** within the E1 component of the BCKDH complex; active sites formed at α–β′ interfaces (pqac-00000003, pqac-00000004, pqac-00000006) | **ThDP/TPP**; **K+** stabilizing site in β subunit (pqac-00000003, pqac-00000006, pqac-00000008) | Branched-chain α-ketoacids: **KIC** (2-oxoisocaproate, from leucine), **KMV** (2-oxo-3-methylvalerate, from isoleucine), **KIV** (2-oxoisovalerate, from valine) (pqac-00000001, pqac-00000002) | Corresponding branched-chain acyl-CoAs after oxidative decarboxylation: **isovaleryl-CoA**, **α-methylbutyryl-CoA**, **isobutyryl-CoA** + **CO2** (via transfer to lipoyl-E2 during the BCKDH reaction) (pqac-00000001, pqac-00000002) | Primarily **mitochondrial matrix** as part of the BCKDH complex; recent cardiac evidence also supports an **extramitochondrial/ER-associated pool** (pqac-00000019, pqac-00000024, pqac-00000025, pqac-00000026) | **THDP-binding** and **transketolase-like** domains; β subunit contributes residues required for cofactor binding, metal coordination, and E2 interaction (pqac-00000006, pqac-00000007) | **Maple syrup urine disease (MSUD) type 1B** caused by pathogenic **BCKDHB** variants; major disease gene in multiple population studies (pqac-00000030, pqac-00000031, pqac-00000032, pqac-00000000) | BCKDH complex is inhibited by **BCKDK-mediated phosphorylation** of the E1α subunit and activated by **PPM1K/PP2Cm-mediated dephosphorylation**; BCKAs such as KIC allosterically suppress BCKDK (pqac-00000018, pqac-00000019, pqac-00000020) |


*Table: This table summarizes core molecular, biochemical, structural, localization, and disease-related properties of human BCKDHB. It is useful as a compact reference for functional annotation of the BCKDHB gene product within the BCKDH complex.*