ID   2.3.1.328
DE   branched-chain 2-oxoacid:malonyl-[acyl-carrier protein] acyltransferase.
CA   N(6)-[(R)-lipoyl]-L-lysyl-[lipoyl-carrier protein] + 4-methyl-2-
CA   oxopentanoate + malonyl-[ACP] + 2 H(+) = 5-methyl-3-oxohexanoyl-[ACP] +
CA   N(6)-[(R)-dihydrolipoyl]-L-lysyl-[lipoyl-carrier protein] + 2 CO2.
CC   -!- The enzyme, characterized from an environmental DNA sample and
CC       expressed in Paraburkholderia graminis, is a complex enzyme whose
CC       purpose is to divert branched-chain 2-oxo acids to production of
CC       branched-chain N-acyl amino acids by producing branched 3-oxoacyl-
CC       [ACP] molecules.
CC   -!- NasB accepts branched-chain 2-oxoacids such as 4-methyl-2-
CC       oxopentanoate, and catalyzes a decarboxylative transfer to a thiamine
CC       diphosphate cofactor, followed by a transfer to a lipoyl cofactor,
CC       and finally a second decarboxylative transfer to the malonyl-[ACP]
CC       acceptor.
CC   -!- The products, such as 5-methyl-3-oxohexanoyl-[ACP], can be extended
CC       by the fatty acid synthase system to form branched long-chain fatty-
CC       acyl-[ACP] molecules, which serve as substrates for EC 2.3.1.327.
CC   -!- During the reaction the lipoyl cofactor is reduced to dihydrolipoyl,
CC       which must be oxidized back to lipoyl by an unknown enzyme.
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