Characterisation of a solvent-tolerant haloarchaeal (R)-selective transaminase isolated from a Triassic period salt mine

Stephen A Kelly,Julianne Megaw,John W Mcgrath,Damian J Magill,Christopher C R Allen,Thorsten Allers,Timofey Skvortsov,Brendan F Gilmore,Thomas S Moody

doi:10.1007/s00253-019-09806-y

Abstract

Transaminase enzymes (TAms) are becoming increasingly valuable in the chemist’s toolbox as a biocatalytic route to chiral amines. Despite high profile successes, the lack of (R)-selective TAms and robustness under harsh industrial conditions continue to prove problematic. Herein, we report the isolation of the first haloarchaeal TAm (BC61-TAm) to be characterised for the purposes of pharmaceutical biocatalysis. BC61-TAm is an (R)-selective enzyme, cloned from an extremely halophilic archaeon, isolated from a Triassic period salt mine. Produced using a Haloferax volcanii–based expression model, the resulting protein displays a classic halophilic activity profile, as well as thermotolerance (optimum 50 °C) and organic solvent tolerance. Molecular modelling predicts the putative active site residues of haloarchaeal TAms, with molecular dynamics simulations providing insights on the basis of BC61-TAm’s organic solvent tolerance. These results represent an exciting advance in the study of transaminases from extremophiles, providing a possible scaffold for future discovery of biocatalytic enzymes with robust properties.

Highlights

Chiral amines are valuable building blocks for the pharmaceutical industry, representing versatile intermediates in the synthesis of active pharmaceutical ingredients (APIs)
We describe a Transaminase enzymes (TAms) from a haloarchaeon, Halorubrum sp
Of the 19 results obtained using the search term ‘aminotransferase’, those belonging to pyridoxal phosphate (PLP) fold types I and IV were selected for further study, as they are known to be industrially relevant (Steffen-Munsberg et al 2015)

Summary

Introduction

Chiral amines are valuable building blocks for the pharmaceutical industry, representing versatile intermediates in the synthesis of active pharmaceutical ingredients (APIs). Their synthesis using conventional chemical means can suffer from a number of critical drawbacks, including the need for volatile. Nottingham, UK 4 Almac, Department of Biocatalysis & Isotope Chemistry, 20 Seagoe. Industrial Estate, Craigavon, UK 5 Arran Chemical Company Limited, Unit 1 Monksland Industrial. Biocatalytic routes to optically active amines have emerged as a ‘green’ alternative to conventional synthetic chemistry approaches, expanding the chemist’s toolbox and affording an economically viable approach for the production of these valuable compounds. The ability of biocatalysts to operate in aqueous media, as well as at ambient temperature and neutral pH, makes them extremely desirable and useful in streamlining API synthesis

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Results

Conclusion