Ring fission of anthracene by a eukaryote

Area of Science:

• Environmental microbiology
• Biotechnology
• Bioremediation

Background:

• Ligninolytic fungi possess a unique ability to degrade polycyclic aromatic hydrocarbons (PAHs).
• The specific enzymatic mechanisms, particularly the role of lignin peroxidases (LiPs) in vivo PAH degradation, remain largely unknown.
• Understanding these pathways is crucial for bioremediation applications.

Purpose of the Study:

• To elucidate the metabolic pathway of anthracene (AC) degradation in the ligninolytic fungus Phanerochaete chrysosporium.
• To investigate the role of lignin peroxidases (LiPs) in the initial oxidation of AC to 9,10-anthraquinone (AQ).
• To determine if LiPs are essential for the in vivo degradation of PAHs.

Main Methods:

• Utilized chromatographic and isotope dilution techniques to track anthracene (AC) and 9,10-anthraquinone (AQ) metabolism.
• Cultured Phanerochaete chrysosporium under specific ligninolytic conditions.
• Analyzed ring-fission metabolites, specifically phthalic acid, to identify degradation intermediates.

Main Results:

• Phanerochaete chrysosporium rapidly oxidized anthracene (AC) to 9,10-anthraquinone (AQ).
• Both AC and AQ were significantly mineralized, with phthalic acid identified as a common ring-fission metabolite.
• Phthalate production from AQ was observed exclusively under ligninolytic culture conditions, suggesting enzyme involvement.

Conclusions:

• The primary pathway for anthracene degradation in Phanerochaete chrysosporium is AC → AQ → phthalate + CO2.
• This pathway is likely mediated by lignin peroxidases (LiPs) and other enzymes involved in ligninolytic metabolism.
• These findings provide evidence for the in vivo role of LiPs in initiating PAH degradation by fungi.