Dibenzothiophene Catabolism Proceeds via a Flavin-N5-oxide Intermediate

Area of Science:

• Biochemistry
• Enzymology
• Microbial Metabolism

Background:

• Dibenzothiophene (DBT) is a persistent organosulfur pollutant found in fossil fuels.
• The microbial degradation of DBT is essential for environmental remediation.
• The enzyme DszA catalyzes the third step in the DBT catabolic pathway, converting DBT sulfone.

Purpose of the Study:

• To elucidate the reaction mechanism of the flavoenzyme DszA.
• To identify key intermediates in the conversion of dibenzothiophene sulfone.
• To confirm the role of flavin-N5-oxide in the DszA-catalyzed reaction.

Main Methods:

• Mechanistic studies involving kinetic and spectroscopic analyses.
• Liquid chromatography-mass spectrometry (LC-MS) for intermediate detection.
• Co-elution experiments and (18)O2 labeling studies to confirm intermediate identity.

Main Results:

• The reaction mechanism involves the C2 hydroperoxide of dibenzothiophene sulfone.
• A flavin-N5-oxide intermediate was proposed and detected.
• LC-MS analysis and (18)O2 labeling confirmed the flavin-N5-oxide intermediacy.

Conclusions:

• DszA utilizes a flavin-N5-oxide intermediate for the conversion of dibenzothiophene sulfone.
• This finding provides crucial insights into the enzymatic mechanism of organosulfur compound degradation.
• The study enhances our understanding of microbial pathways for bioremediation of pollutants.