The first, R1, contains a total of 22 atoms and includes the p-coumaric acid chromophore and the S-C bond from the CYS69 residue. The second region, R2, contains all atoms in R1 and additionally, the GLH46 and TYR42 residues. The total number of QM atoms in R2 is 49. The third region, R4, has 159 atoms and contains THR50, ARG52, PHE62, VAL66, ALA67, PRO68, THR70, PHE96, TYR98 in addition to all the atoms in R2. These QM regions contain hydrogen link atoms whenever the QM/MM interface crosses a covalent bond. Note that the nomenclature of QM regions is consistent with previous studies. The MM region of the protein was represented by the ff99SB forcefield and the water molecules In Table , we present the results of all simulations. V100 runs were carried out on a single node containing 4 NVIDIA Volta V100-PCIe (32 GB) type GPUs, Intel Xeon(R) Platinum 8260 (2.40GHz) CPUs and 178 GB memory. For A100 runs, a node containing memory was used. Both nodes were located in the high performance computing center (iCER HPCC) at Michigan State University. Simulations on AMD GPUs were performed on the AMD cloud platform, specifically, on a node containing 8 AMD Instinct MI100 (32 GB) type GPUs, AMD EPYC 7742 64-Core (2.25 GHz) CPUs and 512 GB memory. The code was compiled on NVIDIA platforms with CUDA/11.4.2, GCC/9.3.0 and OpenMPI/4.0.3. The AMD version was compiled using ROCM/5.3.0 with the same GCC and OpenMPI versions. Magma/2.6.2 was also used in the AMD version. For each simulation, an equal number of CPU cores and GPUs was used. For comparison, the V100/A100/MI100 GPUs have a peak FP64 performance of 7.8/9.7/11.5 TFLOPs and a global memory bandwidth of 0.9/1.6/1.2 TB/s.