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EC 1.2.1.25 Details
EC number
1.2.1.25
Accepted name
branched-chain α-keto acid dehydrogenase system
Reaction
3-methyl-2-oxobutanoate + CoA + NAD+ = 2-methylpropanoyl-CoA + CO2 + NADH
Other name(s)
branched-chain α-keto acid dehydrogenase complex, 2-oxoisovalerate dehydrogenase, α-ketoisovalerate dehydrogenase, 2-oxoisovalerate dehydrogenase (acylating)
Systematic name
3-methyl-2-oxobutanoate:NAD+ 2-oxidoreductase (CoA-methylpropanoylating)
CAS registry number
37211-61-3
Comment
This enzyme system catalyses the oxidative decarboxylation of branched-chain α-keto acids derived from L-leucine, L-isoleucine, and L-valine to branched-chain acyl-CoAs. It belongs to the 2-oxoacid dehydrogenase system family, which also includes EC 1.2.1.104, pyruvate dehydrogenase system, EC 1.2.1.105, 2-oxoglutarate dehydrogenase system, EC 1.4.1.27, glycine cleavage system, and EC 2.3.1.190, acetoin dehydrogenase system. With the exception of the glycine cleavage system, which contains 4 components, the 2-oxoacid dehydrogenase systems share a common structure, consisting of three main components, namely a 2-oxoacid dehydrogenase (E1), a dihydrolipoamide acyltransferase (E2), and dihydrolipoamide dehydrogenase (E3). The reaction catalysed by this system is the sum of three activities: EC 1.2.4.4, 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring), EC 2.3.1.168, dihydrolipoyllysine-residue (2-methylpropanoyl)transferase, and EC 1.8.1.4, dihydrolipoyl dehydrogenase. The system also acts on (S)-3-methyl-2-oxopentanoate and 4-methyl-2-oxopentanoate.
History
created 1972, modified 2019, modified 2020
EC Tree
1.2.1.1 created 1961, modified 1982, modified 2002, deleted 2005
1.2.1.6 created 1961, deleted 1965
1.2.1.14 created 1961, deleted 1984
1.2.1.34 created 1972, deleted 1983 [transferred to EC 1.1.1.180, deleted 1984]
1.2.1.35 created 1972, deleted 1984
1.2.1.37 created 1972, deleted 1984
1.2.1.55 created 1990, deleted 2003
1.2.1.56 created 1990, deleted 2003