Oxidosqualene cyclase involved in the biosynthesis of lupeol. Required for the production of betulinic acid. (S)-2,3-epoxysqualene = lupeol Expressed in root nodules. Low expression in developing seedlings. Down-regulated by methyl jasmonate (MeJA). No effect of gibberellin A3 (GA3). Belongs to the terpene cyclase/mutase family.