ABSTRACT
Imine reductases (IRED) are fascinating enzymes, because the asymmetric reduction of C=N-double bonds represents a very atom-efficient approach to prepare chiral amines and amino acid derivatives. The group of NADPH-dependent IREDs suitable for biocatalytic applications are members of the 6-phosphogluconate reductases family. Reductive amination allows in theory a quite modular synthesis of different product scaffolds, as structurally different ketones can be combined with either primary or secondary amine substrates as nucleophiles to yield secondary or tertiary chiral amine products. Enzymatic reduction of C=N double bond takes place in several natural pathways, such as the biosynthesis of cofactors, in the amino acid metabolism of lysine and proline, as well as the synthesis of diverse natural alkaloid products. Aldehydes belong to the preferred group of substrates in reductive amination by employing both IREDs or RedAms, but when employing linear aldehydes, no stereo center will be created during the reaction.
