An Unexpected Oxidosqualene Cyclase Active Site Architecture in the Multifunctional α-Amyrin Synthase.

Ordered polycyclization catalyzed by oxidosqualene synthases (OSCs) morph a common linear precursor into structurally complex and diverse triterpene scaffolds with varied bioactivities. We identified three OSCs from . ItOSC2 is a rare multifunctional α-amyrin synthase.