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Tolerance of β‐diketone hydrolases as representatives of the crotonase superfamily towards organic solvents

Crotonase superfamily enzymes catalyze a wide variety of reactions, including hydrolytic C–C bond cleavage in symmetrical β‐diketones by 6‐oxo camphor hydrolase (OCH) from Rhodococcus sp. The organic solvent tolerance and temperature stability of OCH and its structurally related ortholog Anabaena β‐diketone hydrolase have been investigated. Both enzymes showed excellent tolerance toward organic solvents; for instance, even in the presence of 80% (v/v) THF or dioxane, OCH was still active. In most solvent mixtures, except methanol, the stereospecificity was conserved (>99% e.e. of product), hence neither the type of solvent nor its concentration appeared to have an effect on the stereoselectivity of the enzyme. Attempts to correlate the observed activities with log P, functional solvent group or denaturing capacity (DC) of the solvent were only successful in the case of DC for water miscible solvents. This study represents the first investigation of organic solvent stability for members of the crotonase superfamily. Biotechnol. Bioeng. 2011;108: 2815–2822. © 2011 Wiley Periodicals, Inc.