A putative Fe2+-bound persulfenate intermediate in cysteine dioxygenase.

Area of Science:

• Biochemistry
• Enzymology
• Structural Biology

Background:

• Reactions of dioxygen, superoxide, and hydroperoxides with thiolates are known to involve persulfenate intermediates.
• These persulfenate intermediates have never been directly visualized, limiting mechanistic understanding.

Purpose of the Study:

• To visualize and characterize the elusive persulfenate intermediate in enzymatic reactions.
• To elucidate the mechanism of cysteine dioxygenase (CDO) and its role in thiol oxidation.

Main Methods:

• High-resolution (1.4 Å) crystal structure determination of the Fe(2+)-dependent enzyme cysteine dioxygenase (CDO).
• Trapping and structural analysis of a putative persulfenate intermediate within the enzyme's active site.

Main Results:

• The crystal structure successfully captured a persulfenate intermediate in the active site of CDO.
• A unique three-membered Fe-S-O cyclic intermediate was identified, suggesting a novel oxidation pathway.
• The enzyme's active site environment appears to facilitate the isomerization of the persulfenate to the sulfinate product.

Conclusions:

• This study provides the first direct visualization of a persulfenate intermediate in an enzymatic context.
• The findings challenge existing models of dioxygenase mechanisms and propose a new role for the Fe-proximal oxygen atom.
• The structural data offers critical insights into the catalytic cycle of cysteine dioxygenase and thiol oxidation processes.