Medium-chain specific acyl-CoA dehydrogenase is one of the acyl-CoA dehydrogenases that catalyze the first step of mitochondrial fatty acid beta-oxidation, an aerobic process breaking down fatty acids into acetyl-CoA and allowing the production of energy from fats (PubMed:3233192). The first step of fatty acid beta-oxidation consists in the removal of one hydrogen from C-2 and C-3 of the straight-chain fatty acyl-CoA thioester, resulting in the formation of trans-2-enoyl-CoA (PubMed:3233192). Electron transfer flavoprotein (ETF) is the electron acceptor that transfers electrons to the main mitochondrial respiratory chain via ETF-ubiquinone oxidoreductase (ETF dehydrogenase) (By similarity). Among the different mitochondrial acyl-CoA dehydrogenases, medium-chain specific acyl-CoA dehydrogenase acts specifically on acyl-CoAs with saturated 6 to 12 carbons long primary chains (By similarity). a medium-chain 2,3-saturated fatty acyl-CoA + H(+) + oxidized [electron-transfer flavoprotein] = a medium-chain (2E)-enoyl-CoA + reduced [electron-transfer flavoprotein] H(+) + oxidized [electron-transfer flavoprotein] + pentanoyl-CoA = (2E)-pentenoyl-CoA + reduced [electron-transfer flavoprotein] H(+) + hexanoyl-CoA + oxidized [electron-transfer flavoprotein] = (2E)-hexenoyl-CoA + reduced [electron-transfer flavoprotein] H(+) + octanoyl-CoA + oxidized [electron-transfer flavoprotein] = (2E)-octenoyl-CoA + reduced [electron-transfer flavoprotein] decanoyl-CoA + H(+) + oxidized [electron-transfer flavoprotein] = (2E)-decenoyl-CoA + reduced [electron-transfer flavoprotein] dodecanoyl-CoA + H(+) + oxidized [electron-transfer flavoprotein] = (2E)-dodecenoyl-CoA + reduced [electron-transfer flavoprotein] H(+) + oxidized [electron-transfer flavoprotein] + tetradecanoyl-CoA = (2E)-tetradecenoyl-CoA + reduced [electron-transfer flavoprotein] H(+) + hexadecanoyl-CoA + oxidized [electron-transfer flavoprotein] = (2E)-hexadecenoyl-CoA + reduced [electron-transfer flavoprotein] Lipid metabolism; mitochondrial fatty acid beta-oxidation. Homotetramer (PubMed:12966080). Interacts with the heterodimeric electron transfer flavoprotein ETF (By similarity). Acetylated. Could occur at proximity of the cofactor-binding sites and reduce the catalytic activity. Could be deacetylated by SIRT3. Belongs to the acyl-CoA dehydrogenase family.