Reaction Mechanism of Human Renin Studied by Quantum Mechanics/Molecular Mechanics (QM/MM) Calculations

In this paper, we present the catalytic mechanism of human renin computationally investigated using an ONIOM quantum mechanics/molecular mechanics (QM/MM) methodology (B3LYP/6-31G(d):AMBER), with final energies calculated at the M06/6-311++G(2d,2p):AMBER level of theory. It was demonstrated that the full mechanism involves three sequential steps: (i) a nucleophilic attack of a water molecule on the carbonyl carbon of the scissile bond, resulting in a very stable tetrahedral gem-diol intermediate; (ii) a protonation of the peptidic bond nitrogen; and (iii) a complete breakage of the scissile bond. The activation energy barrier obtained for the angiotensinogen hydrolysis by renin was calculated as 22.0 kcal mol(-1), which is consistent with the experimental value, albeit slightly larger. We have shown also that the cleavage of a mutated substrate (Val10Phe) occurs in a manner similar to that of the wild-type substrate. These results provide an understanding of the reaction catalyzed by human renin with atomistic detail. This is of particular importance because this enzyme plays a special role in the control of the reninangiotensin system and, consequently, it is at the center of current hypertension therapy.