Site-directed mutagenesis of β sesquiphellandrene synthase enhances enzyme promiscuity

The chemical formation of terpenes in nature is carried out by terpene synthases as the main biocatalysts to guide the carbocation intermediate to form structurally diverse compounds including acyclic, mono- and multiple cyclic products. Despite intensive study of the enzyme active site, the mechanism of specific terpene biosynthesis remains unclear. Here we demonstrate that a single mutation of the amino acid L454G or L454A in the active site of Persicaria minor beta-sesquiphellandrene synthase leads to a more promiscuous enzyme that is capable of producing additional hydroxylated sesquiterpenes such as sesquicineole, sesquisabinene hydrate and alpha-bisabolol. Furthermore, the same L454 residue mutation (L454G or L454A) in the active site also improves the protein homogeneity compared to the wild type protein. Taken together, our results demonstrate that residue Leucine 454 in the active site of beta-sesquiphellandrene synthase is important for sesquiterpene product diversity as well as the protein homogeneity in solution.