Investigating the Regioselectivity and Catalysis Action of Cytochrome P450

Abstract

In this thesis, we have studied two aspects of Cytochrome P450 with camphor as the substrate. Our initial studies involved studying the regioselectivity of Compound I of P450 using Density Functional Theory calculations on gas phase and cluster models of Compound I and camphor. The regioselectivity at two sites of camphor, namely the 3rd and 5th carbon atoms, have been studied in this thesis for the rate-determining step of hydroxylation reaction by P450. We have also studied the efficiency of catalysis reaction by P450 and how it changes when we go from single-substrate state to multi-substrate state using a combination of Molecular Dynamics and a combination of non-equilibrium QM/MM MD simulations; we used QM/MM Steered Molecular Dynamics along with Umbrella Sampling to sample the complete phase space of the reaction. These simulations have been used to observe the free energy differences in both the P450 states during the first hydrogen atom transfer reaction. The energy difference between the two states indicates that the catalysis reaction is more favoured in the multi-substrate state. The regioselective studies have shown how the enzyme environment affects the kinetics of the reaction and favours exo-hydrogen atom extraction at the 5th carbon of camphor.