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    'Dopamine-first' mechanism enables the rational engineering of the norcoclaurine synthase aldehyde activity profile

    Lichman, B.R. and Gershater, M.C. and Lamming, E.D. and Pesnot, T. and Sula, Altin and Keep, Nicholas H. and Hailes, H.C. and Ward, J.M. (2015) 'Dopamine-first' mechanism enables the rational engineering of the norcoclaurine synthase aldehyde activity profile. FEBS Journal 282 (6), pp. 1137-1151. ISSN 1742-464X.

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    Abstract

    Norcoclaurine synthase (NCS) (EC 4.2.1.78) catalyzes the Pictet–Spengler condensation of dopamine and an aldehyde, forming a substituted (S)-tetrahydroisoquinoline, a pharmaceutically important moiety. This unique activity has led to NCS being used for both in vitro biocatalysis and in vivo recombinant metabolism. Future engineering of NCS activity to enable the synthesis of diverse tetrahydroisoquinolines is dependent on an understanding of the NCS mechanism and kinetics. We assess two proposed mechanisms for NCS activity: (a) one based on the holo X-ray crystal structure and (b) the ‘dopamine-first’ mechanism based on computational docking. Thalictrum flavum NCS variant activities support the dopamine-first mechanism. Suppression of the non-enzymatic background reaction reveals novel kinetic parameters for NCS, showing it to act with low catalytic efficiency. This kinetic behaviour can account for the ineffectiveness of recombinant NCS in in vivo systems, and also suggests NCS may have an in planta role as a metabolic gatekeeper. The amino acid substitution L76A, situated in the proposed aldehyde binding site, results in the alteration of the enzyme's aldehyde activity profile. This both verifies the dopamine-first mechanism and demonstrates the potential for the rational engineering of NCS activity.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): alkaloid biosynthesis, biocatalysis, enzyme engineering, enzyme kinetics, enzyme mechanism
    School: Birkbeck Schools and Departments > School of Science > Biological Sciences
    Research Centre: Structural Molecular Biology, Institute of (ISMB)
    Depositing User: Administrator
    Date Deposited: 09 Mar 2015 17:03
    Last Modified: 06 Dec 2016 10:42
    URI: http://eprints.bbk.ac.uk/id/eprint/11814

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