Functional Analysis of a Rice Oxidosqualene Cyclase through Total Gene Synthesis

Dear Editor, Plants produce a large range of triterpenoids that serve as chemical defenses against pathogens. For example, β-amyrin synthase （AsbAS1） performs the initial enzymatic step in the biosynthesis of the potent antimicrobial avencins in oats （Haralampidis et al., 2001）. Additionally, other triterpenoids such as glycyrrhizin and QS21 are known to have beneficial or detrimental effects for human health （Osbourn et al., 2011）. For some time, heterologous expression of plant oxidos- qualene cyclases （OSCs） in yeast has been a powerful meth- odology for the functional characterization of this important family of triterpene biosynthetic enzymes.