O₂ Activation by Non-Heme Iron Enzymes

Area of Science:

• Biochemistry
• Bioinorganic Chemistry
• Enzymology

Background:

• Non-heme iron enzymes are crucial biological catalysts involved in oxygen activation.
• Studying non-heme iron enzymes has historically been challenging compared to heme enzymes.
• Advancements in spectroscopic methods now allow detailed investigation of their structure-function relationships.

Purpose of the Study:

• To summarize the molecular mechanisms of oxygen activation by non-heme iron enzymes.
• To elucidate the roles of cosubstrates in controlling oxygen activation.
• To describe the oxygen intermediates generated during these enzymatic reactions.

Main Methods:

• Review of current spectroscopic techniques applied to non-heme iron enzyme studies.
• Analysis of reaction mechanisms involving oxygen and cosubstrates.
• Characterization of reactive oxygen intermediates.

Main Results:

• Three distinct modes of oxygen activation by non-heme iron enzymes were identified.
• Non-heme iron reactivity differs from heme enzymes, featuring a low-spin Fe(III)-OOH intermediate.
• Two subclasses generate high-spin Fe(IV)=O intermediates, offering controlled selectivity via frontier molecular orbitals.
• Substrate binding can lead to one-electron reductive activation of O2 to an Fe(III)-superoxide for H-atom abstraction and electrophilic attack.

Conclusions:

• Non-heme iron enzymes employ diverse strategies for oxygen activation, distinct from heme counterparts.
• Understanding these mechanisms and intermediates is key to correlating enzyme structure with function.
• These findings advance the knowledge of biological oxygen chemistry and enzyme catalysis.