Engineering SCP_Q111BpyAla the most promising ArM (SCP_Q111BpyAla) forwards, we chose to use a structurebased alanine scanning approach to see if any of the residues identified from either the computational or structural work impacted activity or selectivity . Each amino acid was substituted individually with alanine via site-directed mutagenesis, and the yields and enantioselectivities in Friedel-Crafts reactions catalysed by these mutant SCP ArMs were determined (Table ). These reactions were carried out at pH 5, as slightly improved enantiomeric ratios were observed compared to those performed at pH 6 (Table None of the mutations screened showed substantial variations (i.e. a complete drop in reactivity or selectivity). Indeed, the mutation with the biggest difference was F34A which was chosen due to its location nearby and within the protein hydrophobic pocket (Table , entry 4). SCP_Q111BpyAla F34A exhibited substantial precipitation suggesting that disruption to the protein core reduced stability, leading to the observed low activity and selectivity. A similar rationale was also used for the choice of V82A which gave lower activity and selectivity but not to the same extent (Table , entry 3 and 4). The crystal structure suggested that K115 and D88 may play a role in stabilising the bipyridine position within the protein through aromatic- electrostatic interactions. Mutating D88 to gave no meaningful in enantioselectivity (Table , entry 7), whilst K115A showed a reduction in enantioselectivity (Table , entry 6). The more flexible nature of the lysine side chain means it is less clear if this can be attributed to structural changes as opposed to some role with substrate binding. The computational work revealed no interaction of the substrates with K115. In contrast, a close contact between the side chain of D88 and the copper atom was observed in the modelled transition states and D88 was shown to participate in water bonding networks with the substrates. Both these interactions would be disrupted on mutation of D88 to alanine, suggesting that either these interactions are of minor importance in catalysis or alternative residues such as Q108 could replace the hydrogen bonding interactions with water. Whilst Q108A was shown to reduce the enantioselectivity obtained with SCP-Q111BpyAla experimentally (Table , entry 2), no clear role was observed in the computational work.