Science, Vol.275, No.5299, 515-518, 1997
An (Fe2O2)-O-IV Diamond Core Structure for the Key Intermediate Q of Methane Monooxygenase
A new paradigm for oxygen activation is required for enzymes such as methane monooxygenase (MMO), for which catalysis depends on a nonheme diiron center instead of the more familiar Fe-porphyrin cofactor. On the basis of precedents from synthetic diiron complexes, a high-valent Fe-2(mu-O)(2) diamond core has been proposed as the key oxidizing species for MMO and other nonheme diiron enzymes such as ribonucleotide reductase and fatty acid desaturase. The presence of a single short Fe-O bond (1.77 angstroms) per Fe atom and an Fe-Fe distance of 2.46 angstroms in MMO reaction intermediate Q, obtained from extended x-ray absorption fine structure and Mossbauer analysis, provides spectroscopic evidence that the diiron center in Q has an (Fe2O2)-O-IV, diamond core.
Keywords:METHYLOCOCCUS-CAPSULATUS-BATH;RIBONUCLEOTIDE REDUCTASE;MAGNETIC-PROPERTIES;CATALYTIC CYCLE;DIIRON CENTER;HYDROXYLASE;COMPONENT;OXIDATION;CLUSTER;PURIFICATION