Structural highlights
Function[IPIPR_MENPI] Monoterpene synthase that catalyzes the specific reduction of the 1(2)-double bond of (-)-isopiperitenone to produce (+)-cis-isopulegone. Does not catalyze the reverse reaction. Unable to reduce (+)-pulegone, (+)-cis-isopulegone, (-)-menthone or the 1,2-double bond of (-)-carvone. Able to utilize NADH with 20% the efficiency of NADPH. Publication Abstract from PubMedThree enzymes of the Mentha essential oil biosynthetic pathway are highly homologous, namely the ketoreductases (-)-menthone:(-)-menthol reductase and (-)-menthone:(+)-neomenthol reductase, and the "ene" reductase isopiperitenone reductase. We identified a rare catalytic residue substitution in the last two, and performed comparative crystal structure analyses and residue-swapping mutagenesis to investigate whether this determines the reaction outcome. The result was a complete loss of native activity and a switch between ene reduction and ketoreduction. This suggests the importance of a catalytic glutamate vs. tyrosine residue in determining the outcome of the reduction of alpha,beta-unsaturated alkenes, due to the substrate occupying different binding conformations, and possibly also to the relative acidities of the two residues. This simple switch in mechanism by a single amino acid substitution could potentially generate a large number of de novo ene reductases. Pinpointing a Mechanistic Switch Between Ketoreduction and "Ene" Reduction in Short-Chain Dehydrogenases/Reductases.,Lygidakis A, Karuppiah V, Hoeven R, Ni Cheallaigh A, Leys D, Gardiner JM, Toogood HS, Scrutton NS Angew Chem Int Ed Engl. 2016 Aug 8;55(33):9596-600. doi: 10.1002/anie.201603785. , Epub 2016 Jul 13. PMID:27411040[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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This page was last modified 14:00, 10 September 2016.