Phase II metabolism in xenobiotic biotransformation: general mechanisms and the underestimated role of microbial systems

Microbial phase II biotransformation, involving conjugation reactions such as glycosylation, sulfation, and glucuronidation, is increasingly recognized as a valuable in vitro model for mammalian xenobiotic metabolism, particularly drug metabolism. Fungi, especially Cunninghamella species, demonstrate a notable capacity to produce conjugated metabolites, while bacteria also contribute to this process. Although microbial pathways often parallel mammalian metabolism, key differences exist – for example, glycosylation predominates in microbes, whereas glucuronidation is more common in mammals. Microbial biotransformation enables the production of novel and rare metabolites with potentially enhanced pharmacological properties and provides an efficient, eco-friendly alternative to complex chemical synthesis. Furthermore, microorganisms play a significant role in the detoxification and bioremediation of xenobiotics by increasing solubility and reducing toxicity of harmful compounds. Despite some limitations and discrepancies compared to mammalian systems, microbial models offer valuable tools for drug development, metabolite production, and environmental applications. Continued research into the enzymatic mechanisms, metabolic diversity, and ecological roles of microbial phase II pathways is essential to fully exploit their potential in pharmaceutical and environmental sciences.