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Micronutrient Information Center

Fatty-acid Beta-oxidation and the Electron Transfer Flavoprotein System

Multiple acyl-coenzyme A dehydrogenase deficiency (MADD) is caused by mutations in the genes coding for the electron transfer flavoprotein (ETF) and the electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-QO). These flavoproteins are essential for electron transfer from the fatty-acid beta-oxidation (b-oxidation) pathway to the respiratory chain: FAD is the electron acceptor for acyl-CoA dehydrogenase (first step in fatty acid beta-oxidation), and it donates electrons to ETF-FAD, reducing it to ETF-FADH2. The flavoprotein is restored to its oxidized form by ETF-QO, which transfers the electrons to Coenzyme Q10, via its iron-sulfur (Fe-S) cluster and FAD.

CoA, Coenzyme A; Q, Coenzyme Q10/Ubiquinone; Flavin adenine dinucleotide, FAD; Reduced FAD, FADH2