Asparagine and Glutamine Residues Participate in Protein Covalent Binding by Epoxide Metabolite of 8-Epidiosbulbin E Acetate In Vitro and In Vivo

Abstract

Dioscorea Bulbifera L. (DBL), an effective traditional Chinese medicine, has been restricted because of multiple reports that it can cause severe hepatotoxicity. 8-Epidiosbulbin E acetate (EEA), one of the main components of DBL, can induce severe liver injury. It has been reported that EEA can be metabolized by CYP3A to the corresponding cis-enedial intermediate which alkylates the lysine residues of proteins to form pyrroline derivatives. The present study unexpectedly found that the reactive intermediate reacted with the amide groups of asparagine (Asn) and glutamine (Gln) residues of hepatic proteins of mice treated with EEA. The amide-derived protein modification increased with the increase in the dose administered. Like the adduction of the primary amine of lysine residues, the electrophilic metabolite reacted with the amide groups of Asn and Gln residues to offer the corresponding pyrrolines. The structures of the pyrrolines were confirmed by mass spectrometry and nuclear magnetic resonance spectroscopy.

Insight into Janus kinases specificity: From molecular architecture to cancer therapeutics

“…As is well known, proteins, apart from cysteine, contain other amino acids capable of forming covalent bonds with small molecule inhibitors 208,285,286 . Some of these amino acids include asparagine, 287 glutamate, 288 histidine, 289 lysine, 290 methionine, 291 serine, 209 and tyrosine 292 . While covalent small molecule inhibitors specific to these residues of JAKs have not yet been found, these amino acids offer potential for the development of corresponding covalent small molecule inhibitors.…”

Chemical nature of metabolic activation of natural products in traditional Chinese medicines possibly associated with toxicities

“…8-Epidiosbulbin E acetate (EEA), a furanoterpenoid, is another component of Dioscorea bulbifera L. EEA can be metabolized by CYP3A to form the corresponding cis -enedial electrophilic intermediate, which then undergoes condensation reactions with GSH and/or N -acetyl-lysine (NAL) to yield cyclic GSH/NAL conjugates [59,60] . Additionally, the corresponding cis -enedial intermediate can alkylate the lysine, asparagine, and glutamine residues of proteins to form pyrroline derivatives [61,62] . Furthermore, EEA-derived biological amine adducts were detected in mouse liver microsomal incubations, cultured mouse primary hepatocytes, and mice treated with EEA [63] .…”

Covalent inhibitors: An ambitious approach for the discovery of newer oncotherapeutics

“…Aspirin, for instance, serve as a prototype drug that acts through covalent inhibition of cyclooxygenase (COX) enzymes (Patrono, 2023). Subsequently, several covalent drugs with favorable safety profiles were introduced, including penicillin (Zhang et al, 2022), fosfomycin (Nordmann et al, 2022), clavulanic acid, tazobactam (Brown et al, 1996), omeprazole (Poole, 2001), lansoprazole (Wallmark et al, 1984), selegiline, and tranylcypromine (Table 1, Figure 2) (Khushboo et al, 2022; Laux et al, 1995). Interestingly, many of these drugs were approved without a complete understanding of their mechanism of action, and the covalent modification of their targets was identified much later (Robertson, 2005).…”