The oxygen reduction reaction on [NiFe] hydrogenases

Area of Science:

• Biochemistry
• Catalysis
• Computational Chemistry

Background:

• Hydrogen oxidation/evolution catalysts require high oxygen tolerance.
• [NiFe] hydrogenases exhibit remarkable O2-tolerance and rapid active site reactivation.
• Understanding the mechanism of oxygen interaction with these enzymes is crucial for catalyst design.

Purpose of the Study:

• To elucidate the mechanism of oxygen reduction on the active site of [NiFe] hydrogenases.
• To identify the rate-determining step in the oxygen reduction reaction (ORR).
• To explain the differential reactivation rates observed in different active site states.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• A free energy diagram for the ORR was computed.
• The stability of different active site intermediates was analyzed.

Main Results:

• The rate-determining step for ORR was identified as the Ni-B to Ni-SIb' transition.
• The calculations provide an explanation for the slower reactivation of the Ni-A state compared to the Ni-B state.
• The enhanced stability of the Ni-A state structure was found to be the cause of its slow reactivation.

Conclusions:

• The study provides a detailed mechanistic understanding of oxygen reduction in [NiFe] hydrogenases.
• The findings offer insights into the factors governing oxygen tolerance and reactivation kinetics.
• This work can guide the development of more robust hydrogen oxidation/evolution catalysts.