Addressing Serine Lability in a Paramagnetic Dimethyl Sulfoxide Reductase Catalytic Intermediate

Area of Science:

• Bioinorganic Chemistry
• Enzyme Catalysis
• Molybdenum Biochemistry

Background:

• Dimethyl sulfoxide reductase (DMSOR) is crucial for biological redox reactions.
• The catalytic cycle involves a paramagnetic high-g split intermediate.
• Understanding this intermediate is key to enzyme mechanism elucidation.

Purpose of the Study:

• To synthesize and characterize novel desoxo molybdenum(V) complexes.
• To model the high-g split intermediate of DMSOR.
• To gain insight into the geometric and electronic structures of EPR-active DMSOR family enzymes.

Main Methods:

• Synthesis of two new desoxo molybdenum(V) complexes.
• Extended X-ray absorption fine structure (EXAFS) analysis.
• Electron paramagnetic resonance (EPR) spectroscopy.

Main Results:

• Characterization of molybdenum(V) complexes as models for the high-g split intermediate.
• EXAFS and EPR data provided insights into geometric and electronic structures.
• A 6-coordinate [(PDT)2Mo(OH)(O_Ser)]- structure was proposed for the high-g split intermediate.

Conclusions:

• The proposed structure features four S donors, a hydroxyl ligand, and a serinate O donor.
• This geometry facilitates substrate access and two-electron reduction.
• The findings advance the understanding of DMSOR enzyme mechanisms and bioinorganic modeling.