Mutational Analysis of Linalool Dehydratase Isomerase Suggests That Alcohol and Alkene Transformations Are Catalyzed Using Noncovalent Mechanisms

Abstract

The interconversion of nonactivated alkenes and alcohols, catalyzed by (de)hydratases, has great potential in biotechnology for the generation of fine and bulk chemicals. LinD is a cofactor-independent enzyme that catalyzes the reversible (de)hydration of the tertiary alcohol (S)-linalool to the triene β-myrcene and also its isomerization to the primary alcohol geraniol. Structure-informed mutagenesis of LinD, followed by activity studies, confirmed essential roles for residues C171, C180, and H129 in water activation for the hydration of β-myrcene to linalool. However, no evidence of covalent thioterpene intermediates was found using either X-ray crystallography, mass spectrometry, or QM/MM nudged elastic band simulations. Labeling and NMR experiments confirmed a role for residue D39 in (de)protonation of the linalool carbon C10 in the isomerization of linalool to geraniol and also the intermediacy of β-myrcene in this isomerization reaction. X-ray, molecular dynamics, and activity studies also suggested a significant role in catalysis for a mobile methionine residue M125, which exists in substantially altered orientations in different mutant structures