Rational design of a lipase to accommodate catalysis of Baeyer?Villiger oxidation with hydrogen peroxide

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Abstract
The mechanism and potential energy surface for the Baeyer–Villiger oxidation of acetone with hydrogen peroxide catalyzed by a Ser105–Ala mutant of Candida antarctica Lipase B has been determined using ab initio and density functional theories. Initial substrate binding has been studied using an automated docking procedure and molecular dynamics simulations. Substrates were found to bind to the active site of the mutant. The activation energy for the first step of the reaction, the nucleophilic attack of hydrogen peroxide on the carbonyl carbon of hydrogen peroxide, was calculated to be 4.4 kcal mol−1 at the B3LYP/6-31+G* level. The second step, involving the migration of the alkyl group, was found to be the rate-determining step with a computed activation energy of 19.9 kcal mol−1 relative the reactant complex. Both steps were found to be lowered considerably in the reaction catalyzed by the mutated lipase, compared to the uncatalyzed reaction. The first step was lowered by 36.0 kcal mol−1 and the second step by 19.5 kcal mol−1. The second step of the reaction, the rearrangement step, has a high barrier of 27.7 kcal mol−1 relative to the Criegee intermediate. This could lead to an accumulation of the intermediate. It is not clear whether this result is an artifact of the computational procedure, or an indication that further mutations of the active site are required. Figure Second TS (18TS) in the Baeyer–Villiger oxidation in a mutant of CALB. Distances in Å