The function of EBP (EBP cholestenol delta-isomerase, Ensembl gene identifier ENSG00000147155) is as follows. Isomerase that catalyzes the conversion of Delta(8)-sterols to their corresponding Delta(7)-isomers a catalytic step in the postlanosterol biosynthesis of cholesterol. {ECO:0000269|PubMed:12760743, ECO:0000269|PubMed:8798407, ECO:0000269|PubMed:9894009}. Component of the microsomal antiestrogen binding site (AEBS), a multiproteic complex at the ER membrane that consists of an association between EBP and 7-dehydrocholesterol reductase/DHCR7 (PubMed:15175332, PubMed:20615952). This complex is responsible for cholesterol-5,6-epoxide hydrolase (ChEH) activity, which consists in the hydration of cholesterol-5,6-epoxides (5,6-EC) into cholestane- 3beta,5alpha,6beta-triol (CT) (PubMed:20615952). The precise role of each component of this complex has not been described yet (PubMed:20615952). {ECO:0000269|PubMed:15175332, ECO:0000269|PubMed:20615952}.