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 Steroid biosynthesis; cholesterol biosynthesis. During interphase, detected on the endoplasmic reticulum and the nuclear envelope. During mitosis, detected on cytoplasmic vesicles. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Binds to the phenylalkylamine calcium-ion antagonist emopamil, an anti-ischemic drug. Belongs to the EBP family.