The catalytic activities of Bpy-containing SCP metalloenzymes were evaluated in the Cucatalysed Friedel-Crafts alkylation of 5-methoxy-1H-indole 3 with 1-(1-methyl-1H-imidazol-2yl)but-2-en-1-one 4, resulting in the product 5, the benchmark reaction for Cu(II) catalysis (Table ) . Enantioselective product formation was only observed in the presence of the Bpycontaining SCP-metalloenzymes. SCP ArMs with BpyAla showed a higher yield (42-45%) compared to the equivalent Cyscoupled Bpy SCP ArMs. Among the novel ArMs, SCP_Q111BpyAla displayed the greatest enantioselectivity with an e.r. of 20:80 (±1), favouring the S enantiomer, and a yield of 42% (Table , entry 9). The BpyAla moiety in this SCP ArM is situated at the centre of one side of the tunnel, in the middle of -helix 5 (Figure and 3A). By contrast, the ArMs with BpyAla situated at either end of the tunnel showed either no enantioselectivity in the case of SCP_A100BpyAla (Table , entry 7), or lower enantioselectivity with a preference for the R enantiomer (Table , entry 8). We hypothesise that the lower selectivity at the entries to the tunnel could be due to increased flexibility and space leading to less defined binding pocket, compared to position Q111 in the centre of the tunnel. While enantioselectivity towards the R enantiomer was observed with all three Cys mutants, it was limited with the best result observed for SCP_A100CBpy which gave a 66:34 ratio (Table , entries 4-6).