Irreversible inhibition of rat hepatic transacetylase activity by N-Arylhydroxamic acids

Marilee J. Wick, Ibrahim Jantan, Patrick E. Hanna

Research output: Contribution to journalArticle

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Abstract

Both N-hydroxy-2-acetamidofluorene (N-OH-AAF) and the heterocyclic analogue, 2-(N-hydroxyacetamido)carbazole (N-OH-AAC), were shown to be mechanism-based irreversible inhibitors (suicide inhibitors) of partially purified rat hepatic N-acetyltransferase (NAT) activity. Although N-OH-AAC exhibited an apparent first-order inactivation rate constant (ki) that was 7-fold lower than that of N-OH-AAF, their relative ki/KD values indicate that N-OH-AAC was the more potent and efficient inactivator of transacetylase activity. Inactivation of NAT activity by these N-arylhydroxamic acids appeared to involve contributions by electrophiles that react with the enzyme subsequent to release from the active site and by electrophiles that remain complexed with the active site. The irreversible nature of the enzyme inactivation was demonstrated by the failure to recover transacetylase activity upon either extensive dialysis or gel filtration of preparations that had been subjected to incubation with N-OH-AAF or N-OH-AAC. The use of the nucleophile N-acetylmethionine to trap the electrophilic reactants formed in the transacetylase-catalyzed bioactivation process resulted in a lower rate and extent of formation of methylthio adducts with N-OH-AAC than with N-OH-AAF. The results of this study indicate that N-OH-AAF and N-OH-AAC have been potential for use as tools in the investigation of rat hepatic transacetylases.

Original languageEnglish
Pages (from-to)1225-1231
Number of pages7
JournalBiochemical Pharmacology
Volume37
Issue number7
DOIs
Publication statusPublished - 1 Apr 1988
Externally publishedYes

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Rats
Acids
Liver
Acetyltransferases
Hydroxyacetylaminofluorene
Catalytic Domain
hydroxide ion
Inhibition (Psychology)
Nucleophiles
Dialysis
Enzymes
2-(N-hydroxyacetamido)carbazole
Suicide
Gel Chromatography
Rate constants
Gels

ASJC Scopus subject areas

  • Pharmacology

Cite this

Irreversible inhibition of rat hepatic transacetylase activity by N-Arylhydroxamic acids. / Wick, Marilee J.; Jantan, Ibrahim; Hanna, Patrick E.

In: Biochemical Pharmacology, Vol. 37, No. 7, 01.04.1988, p. 1225-1231.

Research output: Contribution to journalArticle

Wick, Marilee J. ; Jantan, Ibrahim ; Hanna, Patrick E. / Irreversible inhibition of rat hepatic transacetylase activity by N-Arylhydroxamic acids. In: Biochemical Pharmacology. 1988 ; Vol. 37, No. 7. pp. 1225-1231.
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