Controlling Monoterpene Isomerization by Guiding Challenging Carbocation Rearrangement Reactions in Engineered Squalene-Hopene Cyclases.

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.

Engineering Biocatalysts for the C-H Activation of Fatty Acids by Ancestral Sequence Reconstruction.

Selective, one-step C-H activation of fatty acids from biomass is an attractive concept in sustainable chemistry. Biocatalysis has shown promise for generating high-value hydroxy acids, but to date enzyme discovery has relied on laborious screening and produced limited hits, which predominantly oxidise the subterminal positions of fatty acids. Herein we show that ancestral sequence reconstruction (ASR) is an effective tool to explore the sequence-activity landscape of a family of multidomain, self-sufficient P450 monooxygenases.

Synthesis of protected 3-aminopiperidine and 3-aminoazepane derivatives using enzyme cascades.

Multi-enzyme cascades utilising variants of galactose oxidase and imine reductase led to the successful conversion of N-Cbz-protected l-ornithinol and l-lysinol to l-3-N-Cbz-aminopiperidine and l-3-N-Cbz-aminoazepane respectively, in up to 54% isolated yield. Streamlining the reactions into one-pot prevented potential racemisation of key labile intermediates and led to products with high enantiopurity.

Regio- and Enantio-selective Chemo-enzymatic C-H-Lactonization of Decanoic Acid to (S)-δ-Decalactone.

The conversion of saturated fatty acids to high value chiral hydroxy-acids and lactones poses a number of synthetic challenges: the activation of unreactive C-H bonds and the need for regio- and stereoselectivity. Here the first example of a wild-type cytochrome P450 monooxygenase (CYP116B46 from Tepidiphilus thermophilus) capable of enantio- and regioselective C5 hydroxylation of decanoic acid 1 to (S)-5-hydroxydecanoic acid 2 is reported. Subsequent lactonization yields (S)-δ-decalactone 3, a high value fragrance compound, with greater than 90 % ee.

Unlocked potential of dynamic elements in protein structures: channels and loops.

Enzymes are nature's powerful catalytic proteins to perform reactions with often outstanding activity, selectivity and specificity. Moreover, the access to non-natural functions of biocatalysts can be facilitated by enzyme engineering. While rational approaches are often focused on an enzyme's active site, from random directed evolution we know that further functional hotspots must exist beyond the active site.

Enantioselective Reduction of Citral Isomers in NCR Ene Reductase: Analysis of an Active-Site Mutant Library.

A deeper understanding of the >99 % S-selective reduction of both isomers of citral catalyzed by NCR ene reductase was achieved by active-site mutational studies and docking simulation. Though structurally similar, the E/Z isomers of citral showed a significantly varying selectivity response to introduced mutations. Although it was possible to invert (E)-citral reduction enantioselectivity to ee 46 % (R) by introducing mutation W66A, for (Z)-citral it remained ≥88 % (S) for all single-residue variants.

Variations in the stability of NCR ene reductase by rational enzyme loop modulation.

The engineering of protein stability is of major importance for the application of enzymes in a wide range of industrial applications. Here we study the determinants of the thermo- and solvent stability of the Zymomonas mobilis ene reductase NCR using a rational protein engineering approach based on analyses of structural and sequence data. We designed and created two loop mutants with the aim to increase their overall stability.