Solubilization and identification of essential functional groups of Candida albicans oxidosqualene cyclase

The enzyme properties and location of essential functional groups of solubilized oxidosqualene cyclase of Candida albicans have been studied. We show that the C. albicans enzyme is much more heat-labile compared with Saccharomyces cerevisiae and rat liver cyclases, requires a histidyl residue for enzyme activity, contains an essential thiol residue either close to or in the active site and exhibits a carbocationic mechanism for catalysis, as the enzyme-bound substrate protects the enzyme from inactivation by a site-directed inactivator.