A comparison of the activation free energies between the reference solution and enzymatic environments reveals that the glucagon fibril lowers the barrier by 3.2 kcal•mol - 1 relative to water. By employing the transition-state theory, the corresponding increase in the reaction rate constant can thus be estimated to be about two orders of magnitude (𝒌 𝒄𝒂𝒍𝒄 𝒄𝒂𝒕 ~ 2 × 10 -04 s -1 ) at the experimental temperature. This implies that the reaction in the enzymatic environment proceeds much faster compared to the reaction in the aqueous solution, which is extremely slow ( 𝒌 𝒄𝒂𝒍𝒄 𝒘𝒂𝒕 ~ 1.1 × 10 -06 s -1 ) under normal experimental setup. This strongly provides atomistic evidence of the catalytic effect of glucagon fibril in the esterolysis of p-NPA, in agreement with our previous experimental study.