Spectroscopic studies of oxygen intermediates and peroxide adducts of the multicopper oxidases.
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文摘
The multicopper oxidases catalyze the 4e− reduction of O2 to H2O. Detailed spectral studies have been carried out on the oxygen intermediate of the type I mercury substituted derivative (T1Hg) of one of the multicopper oxidases, laccase, which is prepared by reacting the reduced enzyme with oxygen. The spectroscopic studies include absorption and EPR for characterizing the intermediate, magnetic circular dichroism (MCD) and SQUID susceptibility studies to obtain the ground state magnetic properties, X-ray edge to obtain information on the oxidation state of the coppers, extended x-ray absorption fine structure (EXAFS) to obtain distances between the metal centers. Further, oxygen counting experiments have been performed using isotope ratio mass spectrometry to obtain the number of oxygen atoms produced upon formation of this intermediate. We are thus able to define the geometric and electronic structure of this oxygen intermediate and this will be presented in detail.