Catalyzes the conversion of Delta(8)-sterols to their corresponding Delta(7)-isomers. lathosterol = 5alpha-cholest-8-en-3beta-ol zymosterol = 5alpha-cholesta-7,24-dien-3beta-ol Enzymatic activity is induced by 25-hydroxycholesterol, cholestyramine and lovastatin. Steroid biosynthesis; cholesterol biosynthesis. During interphase, detected on the endoplasmic reticulum and the nuclear envelope. During mitosis, detected on cytoplasmic vesicles. Expressed in liver. Expression in liver is reduced by 70% in 2 years old rats compare to 3 weeks old. Binds to the phenylalkylamine calcium-ion antagonist emopamil, an anti-ischemic drug. Belongs to the EBP family.