The class II diterpene cyclases catalyze protonation-initiated (bi)cyclization reactions that characterize labdane-related diterpenoid biosynthesis. In collaboration with Prof. David Christianson (Univ. Penn), we have provided the first crystal structures for class II diterpene cyclases. From these we have generated significant insights into the underlying determinants of enzymatic catalysis, including the generation of enzymes wherein single residue changes have led to novel product outcome. Our understanding of these enzymatic structure-function relationships appears to be predictive, and led to re-engineering the activity of the class II diterpene cyclases. Moreover, given the similar use of electrophilic reactions with carbocationic intermediates, the generated insights should be more broadly applicable towards class I (di)terpene synthases as well.
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