A high-valent Fe2O2 diamond core structure is proposed as the key oxidizing species in the oxygen activation chemistry of nonheme diiron enzymes such as methane monooxygenase, ribonucleotide reductase, and fatty acid desaturases. Synthetic precedents serve as the basis for this hypothesis, which is consistent with recent EXAFS results on the high-valent intermediate of methane monooxygenase. The structural and reactivity features of this core are compared with those of the heme ferryl, the key oxidizing species in heme enzymes.
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Our work has been generously supported by the National Institutes of Health (GM-38767) and the National Science Foundation (MCB-9405723).