THE EXISTENCE OF 2 OXIDIZED MN(III)MN(III) FORMS OF THERMUS-THERMOPHILUS MANGANESE CATALASE

Variable-field, variable-temperature saturation magnetization experime nts have been used to derive structural information about the catalyti cally active Mn(III)Mn(III) state of the Thermus thermophilus catalase . They reveal that oxidized catalase contained not one but two Mn(III) Mn(III) forms which are in a pi-I-dependent equilibrium as illustrated in the Scheme. The low-pH form is proposed to contain an oxo and carb oxylato bridge Mn(III)Mn(III) center. The high-pH form is proposed to contain a di(mu-oxo)(mu-carboxylate)dimanganese(III).