Finally, production MD runs were performed using a 4 fs time step, facilitated by hydrogen mass repartitioning and the SHAKE algorithm to constrain all bonds containing hydrogen atoms, an 8Å direct space non-bonded cutoff, Langevin temperature control (collision frequency of 1 ps -1 ), and a Berendsen barostat (pressure relaxation time of 1 ps). Note that in addition to the heavy atom restraints described above, for the duration of our equilibration and production simulations, a further 5 kcal mol -1 Å -2 wall restraint was placed on the donor carbon of the substrate and the acceptor oxygen atom of the D229 side chain that kicks when the two atoms are 3.0 Å or greater apart, in order to prevent substrate dissociation from the active site during our molecular dynamics simulations. This application of this restraint also takes into account prior experimental studies of enzymatic Kemp elimination (see the Brønsted plot in Supplementary Figure of ref.