Isolation and Characterisation of a Halotolerant ω‐Transaminase from a Triassic Period Salt Mine and Its Application to Biocatalysis

Abstract

AbstractChiral amines are valuable intermediates for the pharmaceutical industry, with up to 40% of current pharmaceuticals containing an amine functionality. However, their syntheses by conventional chemical methods often suffer from a number of key drawbacks. Transaminases (TAms) are pyridoxal phosphate (PLP) dependent enzymes capable of transferring an amine group to a prochiral ketone, offering a green and economically viable alternative to chiral amine production. Despite some high profile successes, TAms suffer from limited substrate scope and the ability to function under challenging conditions often required in reaction processes. Mining of untapped, extremophilic environments represents a viable approach in the search for novel enzymes. We report the cloning and expression of an (S)‐selective ω‐TAm from a Halomonas sp. (Ad2‐TAm), isolated from an extreme hypersaline environment formed during the Triassic period (circa 220 mya). Ad2‐TAm exhibits an ability to convert a range of structurally diverse aldehyde and ketone substrates, with no decrease in conversion up to 1.5 M (8.8%) NaCl. The enzyme is also tolerant to the presence of organic cosolvents up to 30% and accepts a range of amino donors. These characteristics make Ad2‐TAm a promising candidate for industrial applications, whilst also highlighting the value of extreme environments as a source of novel enzymes for the pharmaceutical industry as a whole.