THE TRINUCLEAR COPPER CLUSTER IN MULTICOPPER OXIDASES

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EPR SPECTRA OF LACCASE AND ASCORBATE OXIDASE WERE MEASURED FROM 3 K TO 300 K AND WERE SIMULATED,SHOWING THAT THE STRUCTURE OF TYPE 2 COPPER CHANGES FROM TETRAGONAL AT LOW TENPERATURE TO TETRAHEDRAL AT HIGH TEMPERATURE BECAUSE OF THE PROTEIN CONFORMATION CHANGE.SQUID WAS ALSO MEASURED FROM 5 K TO 300 K AND THE - 2J VALUE OF THE ANTIFERROMAGNETIC INTERACTION BETWEEN TYPE 3 COPPERS WERE DETERMINED AND WAS FOUND THAT THE TRIPLET STATE IS NOT NEGLIGIBLE AT ROOM TEMPERATURE IN THE CASE OF ASCORBATE OXIDASE.THE CAREFUL INSPECTION OF SQUID,ESR SPECTRA AND RESONANCE RAMAN SPECTRA OF THE INCREASING AMOUNT OF AZIDE ACTION ON LACCASE INDICATED THAT AZIDE IS BOUND TO ONE OF TYPE 3 COPPERS WITH THE END-ON FASHION BY WEAKENING THE INTERACTION IN THE TRINUCLEAR CENTER AND FINALLY BREAKING THE INTERACTION BY EXPELLING THE BRIDGING HYDROXIDE FROM COORDINATION SPHERE.