Stereoselectivity and Structural Characterization of an Imine Reductase (IRED) from Amycolatopsis orientalis

Godwin A. Aleku, Henry Man, Scott P. France, Friedemann Leipold, Shahed Hussain, Laura Toca-Gonzalez, Rebecca Marchington, Sam Hart, Johan P. Turkenburg, Gideon Grogan, Nicholas J. Turner

    Research output: Contribution to journalArticlepeer-review


    The imine reductase AoIRED from Amycolatopsis orientalis (Uniprot R4SNK4) catalyzes the NADPH-dependent reduction of a wide range of prochiral imines and iminium ions, predominantly with (S)-selectivity and with ee's of up to >99%. AoIRED displays up to 100-fold greater catalytic efficiency for 2-methyl-1-pyrroline (2MPN) compared to other IREDs, such as the enzyme from Streptomyces sp. GF3546, which also exhibits (S)-selectivity, and thus, AoIRED is an interesting candidate for preparative synthesis. AoIRED exhibits unusual catalytic properties, with inversion of stereoselectivity observed between structurally similar substrates, and also, in the case of 1-methyl-3,4-dihydroisoquinoline, for the same substrate, dependent on the age of the enzyme after purification. The structure of AoIRED has been determined in an "open" apo-form, revealing a canonical dimeric IRED fold in which the active site is formed between the N- and C-terminal domains of participating monomers. Co-crystallization with NADPH gave a "closed" form in complex with the cofactor, in which a relative closure of domains, and associated loop movements, has resulted in a much smaller active site. A ternary complex was also obtained by cocrystallization with NADPH and 1-methyl-1,2,3,4-tetrahydroisoquinoline [(MTQ], and it reveals a binding site for the (R)-amine product, which places the chiral carbon within 4 Å of the putative location of the C4 atom of NADPH that delivers hydride to the Cî -N bond of the substrate. The ternary complex has permitted structure-informed mutation of the active site, resulting in mutants including Y179A, Y179F, and N241A, of altered activity and stereoselectivity.

    Original languageEnglish
    Pages (from-to)3880-3889
    Number of pages10
    JournalACS Catalysis
    Issue number6
    Publication statusPublished - 3 Jun 2016


    • biocatalysis
    • chiral amine
    • imine reductase
    • NADPH
    • oxidoreductase


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