Acyl-CoA dehydrogenases and acyl-CoA oxidases are two closely related FAD-containing enzyme families that are present inmitochondriaandperoxisomes, respectively. They catalyze the dehydrogenation of acyl-CoA thioesters to the correspondingtrans-2-enoyl-CoA. This review examines the structure of medium chain acyl-CoA dehydrogenase, as a representative of the dehydrogenase family, with respect to the catalytic mechanism and its broad chain length specificity. Comparing the structures of four other acyl-CoA dehydrogenases provides further insights into the structural basis for the substrate specificityof eachof these enzymes. .
