Molecular Mechanism for Regioselectivity of P450-BM3 Monooxygenase Towards Stearic Acid Hydroxylation

Hydroxy stearic acid is an important raw material for the synthesis of biobased materials, and the hydroxylation at different positions showed different properties. With the catalysis of P450-BM3 monooxygenase, ( ω - 1)-Hydroxy stearic acid was generated, which is a precursor of macrocyclic musk. Experimental results have shown that the L188Q mutant can increase the yield of ( ω - 1)-Hydroxy stearic acid by more than three times, but the reason and underlying molecular mechanism are still unclear. In this study, molecular dynamics (MD) simulations were conducted to study the structural characteristics of the P450-BM3 wild type and its three mutants (F87V, L188Q, and F87V-L188Q) in combination with stearic acid. The MD simulation results showed significant changes in the interactions between the three mutants and the carboxyl- and terminal-end of stearic acid. The results of the Molecular mechanics-Poisson-Boltzmann surface area (MMPBSA) binding free energies indicated that the L188Q mutant showed the most stable binding with the stearic acid. Finally, the H-abstraction free energy barriers of L188Q and wild type systems were calculated to study the regioselectivity, and the results indicated that the L188Q mutant shown a significant advantage in the hydroxylation of stearic acid at the ω - 1 position. Our research results not only explain molecular mechanism for regioselectivity of P450-BM3 towards stearic acid hydroxylation, but also provide some useful ideas for the synthesis of biobased materials from hydroxy fatty acids.