HADH, which belongs to the family of oxidoreductases, is important for converting certain fats to energy. This protein is an enzyme that catalyzes the chemical reaction. ((S)-3-hydroxyacyl-CoA + NAD+ <=>3- oxoacyl-CoA + NADH + H+ ) It is also involved in a process called fatty acid oxidation, in which several enzymes work in a step-wise fashion to break down (metabolize) fats and convert them to energy.