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ADP‐ribose pyrophosphatase‐I partially purified from livers of rats overdosed with acetaminophen reveals enzyme inhibition in vivo reverted in vitro by dithiothreitol
Author(s) -
Ribeiro João Meireles,
Costas María Jesús,
Cameselle José Carlos
Publication year - 1999
Publication title -
journal of biochemical and molecular toxicology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.526
H-Index - 58
eISSN - 1099-0461
pISSN - 1095-6670
DOI - 10.1002/(sici)1099-0461(1999)13:3/4<171::aid-jbt7>3.0.co;2-v
Subject(s) - acetaminophen , dithiothreitol , chemistry , in vivo , buthionine sulfoximine , glutathione , biochemistry , metabolite , poly adp ribose polymerase , in vitro , pharmacology , enzyme , biology , microbiology and biotechnology , polymerase
Abstract Free ADP‐ribose reacts nonenzymatically with proteins and can lead to intracellular damage. The low‐K m ADP‐ribose pyrophosphatase‐I (ADPRibase‐I) is well suited to control free ADP‐ribose and nonenzymatic ADP‐ribosylation. In vitro, the acetaminophen metabolite N‐acetyl‐p‐benzoquinoneimine (NAPQI) decreases ADPRibase‐I V max and increases K m , effects not reverted by dithiothreitol (DTT) and attributed to enzyme arylation. The present study was conducted to test whether acetaminophen overdose affected ADPRibase‐I in vivo. Rats pretreated with 3‐methylcholanthrene and L‐buthionine‐[S,R]‐sulfoximine to potentiate acetaminophen toxicity received an intraperitoneal dose of either acetaminophen (800 mg/kg; n = 5) or vehicle (n = 3). ADPRibase‐I partially purified from acetaminophen‐overdosed rats showed a decreased V max (0.32 ± 0.09 versus 0.60 ± 0.03 mU/mg of liver protein; p < 0.01) not reverted by DTT and an increased K m for ADP‐ribose (1.39 ± 0.31 versus 0.67 ± 0.05 μM; p < 0.01) that, contrary to the in vitro NAPQI effect, was reverted by DTT. Incubation of partially purified ADPRibase‐I from normal rat liver with oxidized glutathione elicited a time‐ and dose‐dependent, DTT‐reverted increase of K m , without change of V max . The results indicate that the activity of ADPRibase‐I can be regulated by thiol exchange and that the increase of K m elicited by acetaminophen overdosage was related to the oxidative stress caused by the drug. It remains to be seen whether an increase of free ADP‐ribose concomitant to ADPRibase‐I inhibition could contribute to the hepatotoxicity of acetaminophen. © 1999 John Wiley & Sons, Inc. J Biochem Toxicol 13: 171–177, 1999