Emerging Metabolic Profiles of Sulfonamide Antibiotics by Cytochromes P450: A Computational–Experimental Synergy Study on Emerging Pollutants

Abstract

Metabolism, especially by CYP450 enzymes, is the main reason for mediating the toxification and detoxification of xenobiotics in humans, while some uncommon metabolic pathways, especially for emerging pollutants, probably causing idiosyncratic toxicity are easily overlooked. The pollution of sulfonamide antibiotics in aqueous system has attracted increasing public attention. Hydroxylation of the central amine group can trigger a series of metabolic processes of sulfonamide antibiotics in humans; however, this work parallelly reported the coupling and fragmenting initiated by amino H-abstraction of sulfamethoxazole (SMX) catalyzed by human CYP450 enzymes. Elucidation of the emerging metabolic profiles was mapped via a multistep synergy between computations and experiments, involving preliminary DFT computations and in vitro and in vivo assays, profiling adverse effects, and rationalizing the fundamental factors via targeted computations. Especially, the confirmed SMX dimer was shown to potentially act as a metabolism disruptor in humans, while spin aromatic delocalization resulting in the low electron donor ability of amino radicals was revealed as the fundamental factor to enable coupling of sulfonamide antibiotics by CYP450 through the nonconventional nonrebound pathway. This work may further strengthen the synergistic use of computations prior to experiments to avoid wasteful experimental screening efforts in environmental chemistry and toxicology.

Direct Electrophilic Attack of Compound I on the Indole Ring in the Peroxygenase Mechanism of Dehaloperoxidase DHP B in Degrading Haloindole: Electron Transfer Promotes the Reaction

“…In addition, the TS and IM (TS1b and IM1b, Figure ) at the lowest lying doublet and quartet states exhibit a slight difference in their electron configurations (Figure ). Theoretical studies of some enzyme-catalyzed reactions , have indicated that the direct O-attack of Cpd I on the benzene or aromatic amine corresponds to a higher barrier than hydrogen abstraction. However, in the case of DHP B in this work, the O-attack on the indole ring by the O atom was calculated to be easier than H-abstraction.…”