VLCAD is an acyl-CoA dehydrogenase (ACAD), which is found in the mitochondria of eukaryotes and in some bacteria. It catalyzes the alpha,beta dehydrogenation of the corresponding trans-enoyl-CoA by FAD, which becomes reduced. The reduced form of ACAD is reoxidized in the oxidative half-reaction by electron-transferring flavoprotein (ETF), from which the electrons are transferred to the mitochondrial respiratory chain coupled with ATP synthesis. VLCAD acts as a homodimer.