A catalytically active [Mn]-hydrogenase incorporating a non-native metal cofactor

Area of Science:

• Bioinorganic chemistry
• Enzyme catalysis
• Biomimetic chemistry

Background:

• Enzymes essential for life utilize specific metal ions for catalysis.
• Hydrogenases, crucial for H2 activation, typically use Nickel (Ni) or Iron (Fe) active sites ([NiFe]-, [FeFe]-, [Fe]-hydrogenases).
• Synthetic systems show other transition metals can catalyze hydrogen production.

Purpose of the Study:

• To develop a biomimetic model of [Fe]-hydrogenase using manganese (Mn) instead of iron (Fe).
• To investigate the catalytic capabilities of this novel manganese-centered complex.
• To assess the functionality and activity of a semi-synthetic [Mn]-hydrogenase.

Main Methods:

• Construction of a biomimetic model complex featuring a manganese active site.
• Testing the model complex for H2 heterolytic cleavage and hydrogenation catalysis.
• Incorporation of the manganese model into an [Fe]-hydrogenase apoenzyme to create a [Mn]-hydrogenase.

Main Results:

• The developed manganese complex successfully cleaved H2 heterolytically and catalyzed hydrogenation reactions.
• The resulting semi-synthetic [Mn]-hydrogenase exhibited enhanced occupancy-normalized activity compared to an analogous [Fe]-hydrogenase.
• Demonstrated catalytic functionality of a non-native metal in a hydrogenase active site.

Conclusions:

• Manganese can serve as a functional active site in hydrogenase enzymes.
• Biomimetic manganese complexes can mimic and even enhance hydrogenase activity.
• Hydrogenases based on manganese active sites are a viable alternative to native iron or nickel enzymes.