Engineering Native Amine Dehydrogenases for the Production of Chiral Amines

Chiral amines are fundamental building blocks in synthetic chemistry routinely used in the production of pharmaceuticals, agrochemicals or in the food industry. In recent years, given the need for more renewable and sustainable approaches to the synthesis of these chiral amines, biocatalysts have been investigated. The consideration of biocatalytic approaches has largely led to enantioselective routes to produce chiral amines often with better yields and less harsh reaction conditions and components. More recently, a class of enzymes, found by sequence driven searches of metagenomic databases and samples, known as native Amine Dehydrogenases (nat-AmDHs) have been used for the asymmetric reductive amination of a range of carbonyl compounds. Herein a selection of nat-AmDHs have been structurally and biochemically studied using a range of techniques such as X-ray crystallography, UV-vis spectrometry, and GC-FID analysis. The canonical structural functionalities of these enzymes were found to be consistent throughout. However, some aspects of these previously uncharacterised nat-AmDHs displayed interesting new properties. Namely the increased active site space in the binding pocket of MATOUAmDH2 which permitted the rational engineering of this enzyme to bind larger, more sterically hindered, substrates to produce pharmaceutically relevant amines such as 2-aminonorbornane. These results provide new knowledge and protein scaffolds for the further engineering of nat-AmDHs for the production of primary and secondary chiral amines of both biological and chemical significance.