Critical Roles of Exchange and Superexchange Interactions inDictating Electron Transfer and Reactivity in Metalloenzymes

Electron transfer (ET) is a fundamental process in transition-metal-dependent metalloenzymes. In these enzymes, the spin-spin interactions within the samemetal center and/or between different metal sites can play a pivotal role in the catalytic cycleand reactivity. This Perspective highlights that the exchange and/or superexchangeinteractions can intrinsically modulate the inner-sphere and long-range electron transfer,thus controlling the mechanism and activity of metalloenzymes. For mixed-valence diironoxygenases, the spin-regulated inner-sphere ET can be dictated by exchange interactions,leading to efficient O-O bond activations. Likewise, the spin-regulated inner-sphere ET canbe enhanced by both exchange and superexchange interactions in [Fe4S4]-dependent SAMenzymes, which enable the efficient cleavage of the SC(gamma)orSC5 ' bond of SAM. Inaddition to inner-sphere ET, superexchange interactions may modulate the long-range ETbetween metalloenzymes. We anticipate that the exchange and superexchange enhancedreactivity could be applicable in other important metalloenzymes, such as Photosystem IIand nitrogenases.

Automated summary

This Perspective highlights the role of exchange and superexchange interactions in modulating electron transfer in metalloenzymes, and suggests their potential applicability in other important metalloenzymes.