Manganese Oxidation State Assignment for Manganese Catalase

Area of Science:

• Biochemistry
• Computational Chemistry
• Enzymology

Background:

• The manganese (III/IV) catalase active site is crucial for reactive oxygen species detoxification.
• Accurate assignment of manganese oxidation states is essential for understanding enzyme mechanisms.

Purpose of the Study:

• To resolve the oxidation state assignment of manganese ions in the superoxidized manganese (III/IV) catalase active site.
• To determine the coordination site of substrate water within the active site.

Main Methods:

• Utilized broken symmetry density functional theory (DFT) calculations.
• Computed hyperfine coupling constants for nitrogen-14, oxygen-17, and hydrogen-1 nuclei.
• Compared calculated hyperfine couplings with experimental data.

Main Results:

• Demonstrated that substrate water coordinates to the Mn(IV) ion.
• Showed that the calculated hyperfine couplings support a different oxidation state assignment than previously proposed.
• Identified the manganese oxidation states as opposite to those suggested by experimental measurements alone.

Conclusions:

• The study corrects the previously assigned oxidation states of manganese ions in the catalase active site.
• Provides a more accurate model for the manganese (III/IV) catalase mechanism.
• Highlights the utility of DFT calculations in refining experimental interpretations of metalloenzyme active sites.