(hī-drok'sē-as'il dē'hī-drō'jen-ā), β-Hydroxyacyl dehydrogenase; an enzyme catalyzing the oxidation of an l-3-hydroxyacyl-CoA to a 3-ketoacyl-CoA with the concomitant reduction of NAD+; one of the enzymes of the β oxidation of fatty acids. Synonym(s): β-ketohydrogenase, β-ketoreductase