[CuOH] + moiety (see reaction II in Fig. ). In a complementary series of experimental and theoretical investigations, we and others have proposed that a tyrosine close to the active site effectively protects LPMOs against the self-oxidation processes by forming a tyrosyl radical (2). The tyrosyl radical (2) can be formed from by reaction I in Fig. where the Cu(II)oxyl species (1) abstracts hydrogen from the hydroxo group of the tyrosine, 40 thus forming a