Enables C-8 sterol isomerase activity. Involved in cholesterol biosynthetic process. Located in intracellular membrane-bounded organelle. Human ortholog(s) of this gene implicated in MEND syndrome; X-linked chondrodysplasia punctata 2; and chondrodysplasia punctata. Orthologous to human EBP (EBP cholestenol delta-isomerase). [provided by Alliance of Genome Resources, Apr 2022]