Engineering Cumene Dioxygenase for Regioselective Hydroxylation of Monoterpenes and Monoterpenoids

Terpenes represent the most abundant class of natural products, with monoterpenes and their hydroxylated derivatives being highly sought after in the flavor and fragrance as well as pharmaceutical industry. However, the selective oxyfunctionalization of these compounds remains challenging. Cumene dioxygenase (CDO) from Pseudomonas fluorescens IP01 has emerged as a promising biocatalyst for monoterpene hydroxylation, though achieving precise regioselectivity control has proven nontrivial. Here, we report the successful engineering of CDO to achieve exceptional regioselective control over this challenging substrate class. The identification of L333A as an important generalist variant proved fundamental, not only enhancing product formation but also opening the way for the conversion of novel monoterpene substrates. Through iterative site‐saturation mutagenesis, we developed enhanced variants which achieved up to 90% selectivity for ( R )‐ and ( S )‐limonene‐10‐ol as well as up to 67% for ( R )‐ and ( S )‐perillyl alcohol while exhibiting additionally improved total product formation. Furthermore, engineered variants significantly broadened the substrate scope of CDO, enabling hydroxylation of all four pinene isomers as well as the monoterpenoids geraniol and (−)‐linalool with selectivities of up to 99%. In summary, this work demonstrates the remarkable potential of tailored Rieske oxygenases for the sustainable production of valuable hydroxylated monoterpenes.