We start by comparing LsAA9 and TaAA9 for the tyrosyl radical (2) formation directly from the Cu(II)-oxyl ( ) intermediate (i.e., reaction I in Fig. ). Next, we compare these two AA9 LPMOs for histidyl radical (3) formation (i.e. reaction II in Fig. ). We finally discuss whether intermediates 2 and 3 can be inter-converted (reaction III in Fig. ) as recently suggested. 41