Browsing by Author "Schneider, Andreas"

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Open Access
Accessing nature's terpenome by squalene-hopene cyclase mediated asymmetric cationic cyclization cascades
(2022) Schneider, Andreas; Hauer, Bernhard (Prof. Dr.)
Die Arbeit befasst sich mit der Erschließung der Squalen-Hopen Zyklase als Biokatalysator für die organische Chemie. Dadurch werden Synthesewege zu hochkomplexen Terpenen stark vereinfacht.
Open Access
Controlling monoterpene isomerization by guiding challenging carbocation rearrangement reactions in engineered squalene‐hopene cyclases
(2024) Ludwig, Julian; Curado‐Carballada, Christian; Hammer, Stephan C.; Schneider, Andreas; Diether, Svenja; Kress, Nico; Ruiz‐Barragán, Sergi; Osuna, Sílvia; Hauer, Bernhard
The interconversion of monoterpenes is facilitated by a complex network of carbocation rearrangement pathways. Controlling these isomerization pathways is challenging when using common Brønsted and Lewis acid catalysts, which often produce product mixtures that are difficult to separate. In contrast, natural monoterpene cyclases exhibit high control over the carbocation rearrangement reactions but are reliant on phosphorylated substrates. In this study, we present engineered squalene‐hopene cyclases from Alicyclobacillus acidocaldarius (AacSHC) that catalyze the challenging isomerization of monoterpenes with unprecedented precision. Starting from a promiscuous isomerization of (+)‐β‐pinene, we first demonstrate noticeable shifts in the product distribution solely by introducing single point mutations. Furthermore, we showcase the tuneable cation steering by enhancing (+)‐borneol selectivity from 1 % to >90 % (>99 % de) aided by iterative saturation mutagenesis. Our combined experimental and computational data suggest that the reorganization of key aromatic residues leads to the restructuring of the water network that facilitates the selective termination of the secondary isobornyl cation. This work expands our mechanistic understanding of carbocation rearrangements and sets the stage for target‐oriented skeletal reorganization of broadly abundant terpenes.
Open Access
Harnessing the structure and dynamics of the squalene‐hopene cyclase for (-)‐ambroxide production
(2023) Schneider, Andreas; Curado, Christian; Lystbaek, Thomas B.; Osuna, Sílvia; Hauer, Bernhard
Terpene cyclases offer enormous synthetic potential, given their unique ability to forge complex hydrocarbon scaffolds from achiral precursors within a single cationic rearrangement cascade. Harnessing their synthetic power, however, has proved to be challenging owing to their generally low catalytic performance. In this study, we unveiled the catalytic potential of the squalene‐hopene cyclase (SHC) by harnessing its structure and dynamics. First, we synergistically tailored the active site and entrance tunnel of the enzyme to generate a 397‐fold improved (-)‐ambroxide synthase. Our computational investigations explain how the introduced mutations work in concert to improve substrate acquisition, flow, and chaperoning. Kinetics, however, showed terpene‐induced inactivation of the membrane‐bound SHC to be the major turnover limitation in vivo. Merging this insight with the improved and stereoselective catalysis of the enzyme, we applied a feeding strategy to exceed 10 5 total turnovers. We believe that our results may bridge the gap for broader application of SHCs in synthetic chemistry.