Importance of Saccharomyces cerevisiae Oxidosqualene-Lanosterol Cyclase Tyrosine 707 Residue for Chair-Boat Bicyclic Ring Formation and Deprotonation Reactions

A contact mapping strategy was applied to identify putative amino acid residues that influence the oxidosqualene-lanosterol B-ring cyclization reaction. A bicyclic intermediate with two altered deprotonation products, in conjunction with lanosterol, were isolated from the ERG7(Y707X) mutants, indicating that the Tyr707 residue may play a functional role in stabilizing the chair-boat bicyclic C-8 cation and the lanosteryl C-8/C-9 cation intermediates.