Covalent binding of acetaminophen to N-10-formyltetrahydrofolate dehydrogenase in mice.
The analgesic acetaminophen is frequently used as a model chemical to study hepatotoxicity; however, the critical mechanisms by which it produces toxicity within the cell are unknown. It has been postulated that covalent binding of a toxic metabolite to crucial proteins may inhibit vital cellular functions and may be responsible for, or contribute to, the hepatotoxicity. To further understand the importance of covalent binding in the toxicity, a major cytosolic acetaminophen-protein adduct of 100 kDa has been purified by a combination of anion exchange chromatography and preparative electrophoresis. N-Terminal and internal amino acid sequences of peptides from the purified 100-kDa acetaminophen-protein adduct were found to be homologous with the deduced amino amino acid sequence from the cDNA of N-10-formyltetrahydrofolate dehydrogenase. Antiserum specific for N-10-formyltetrahydrofolate dehydrogenase and acetaminophen react in a Western blot with the purified 100-kDa acetaminophen-protein adduct. Administration of a toxic dose of acetaminophen (400 mg/kg) to mice resulted in a 25% decrease in cytosolic N-10-formyltetrahydrofolate dehydrogenase activity at 2 hr. The covalent binding of acetaminophen to proteins such as N-10-formyltetrahydrofolate dehydrogenase and the subsequent decreases in their enzyme activity may play a role in acetaminophen hepatotoxicity.
Pumford
N R
NR
Division of Toxicology, University of Arkansas for Medical Sciences, Little Rock, USA.
Halmes
N C
NC
Martin
B M
BM
Cook
R J
RJ
Wagner
C
C
Hinson
J A
JA
D000082:Acetaminophen / Q000378:metabolism* / Q000633:toxicity; D018712:Analgesics, Non-Narcotic / Q000378:metabolism*; D000818:Animals; D008099:Liver / Q000187:drug effects; D008297:Male; D051379:Mice; D008970:Molecular Weight; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism*; D011485:Protein Binding; D000099295:Formyltetrahydrofolate Dehydrogenase
D000082:Acetaminophen; D018712:Analgesics, Non-Narcotic; D000587:Oxidoreductases Acting on CH-NH Group Donors; D000099295:Formyltetrahydrofolate Dehydrogenase