Alkylcysteine Sulfoxide C-S Monooxygenase Uses a Flavin-Dependent Pummerer Rearrangement.

Area of Science:

• Biochemistry
• Enzymology
• Organic Chemistry

Background:

• Flavoenzymes are crucial catalysts in various metabolic pathways, including sulfur compound metabolism.
• S-Alkyl cysteine is a metabolite formed during electrophile detoxification, salvaged by a pathway involving flavoenzymes CmoO and CmoJ.
• CmoJ catalyzes a key C-S bond cleavage in this salvage pathway via an unknown mechanism.

Purpose of the Study:

• To elucidate the reaction mechanism of the flavoenzyme CmoJ.
• To investigate the catalytic strategy employed by CmoJ for S-alkyl cysteine dealkylation.
• To expand the understanding of flavoenzymology in sulfur metabolism.

Main Methods:

• Experimental investigation of the CmoJ reaction mechanism.
• Elimination of proposed carbanion and radical intermediates.
• Characterization of the catalytic pathway through biochemical assays.

Main Results:

• Experimental evidence ruled out carbanion and radical intermediates in the CmoJ reaction.
• The reaction mechanism was determined to proceed via an enzyme-mediated modified Pummerer rearrangement.
• This represents a novel enzymatic transformation for C-S bond cleavage.

Conclusions:

• The mechanism of CmoJ adds a new motif to the flavoenzymology of sulfur metabolism.
• CmoJ employs an unprecedented strategy for the enzyme-catalyzed cleavage of C-S bonds.
• This finding enhances our understanding of microbial metabolic pathways and enzyme catalysis.