Cycloeucalenol cycloisomerase  In enzymology, a cycloeucalenol cycloisomerase () is an enzyme that catalyzes the chemical reaction  Hence, this enzyme has one substrate, cycloeucalenol, and one product, obtusifoliol. This enzyme belongs to the family of isomerases, specifically the class of intramolecular lyases. The systematic name of this enzyme class is cycloeucalenol lyase (cyclopropane-decyclizing). This enzyme is also called cycloeucalenol---obtusifoliol isomerase. This enzyme participates in biosynthesis of steroids.