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N-arylhydroxamic acid N,O-acyltransferase. Positional requirements for the substrate hydroxyl group
Journal of Medicinal Chemistry
|December 1, 1983
Summary
N-Arylhydroxamic acid N,O-acyltransferase (AHAT) enzymes convert toxic N-arylhydroxamic acids into reactive electrophiles. This study found that hydroxyl groups ortho to amide or on the acyl group do not significantly enhance AHAT-catalyzed acyltransferase activity.
Area of Science:
- Biochemistry
- Enzymology
- Toxicology
Background:
- N-Arylhydroxamic acid N,O-acyltransferase (AHAT) is a key enzyme system involved in the metabolism of N-arylhydroxamic acids.
- AHAT can convert toxic and carcinogenic N-arylhydroxamic acids into reactive electrophilic intermediates.
- AHAT also catalyzes the transacetylation of arylamines, a reaction relevant to xenobiotic metabolism.
Purpose of the Study:
- To investigate the role of the N-hydroxyl group in AHAT-catalyzed transacetylation of arylamines.
- To synthesize and evaluate o-hydroxyaryl amides and N-arylglycolamides as potential substrates or modulators of AHAT activity.
- To assess the ability of these compounds to act as acyl donors in AHAT-catalyzed reactions and in the conversion of N-arylhydroxylamines.
Main Methods:
- Synthesis of a series of o-hydroxyaryl amides and N-arylglycolamides.
- Biochemical evaluation of synthesized compounds using partially purified hamster or rat hepatic AHAT.
- Assays for transacetylation of 4-aminoazobenzene and conversion of N-arylhydroxylamines to electrophilic intermediates.
Main Results:
- Several synthesized compounds, including 3-hydroxy-4-acetamidobiphenyl, were weak acetyl donors in AHAT-catalyzed transacetylation.
- Compounds like 1-hydroxy-2-acetamidofluorene and N-arylglycolamides showed less acyl donor activity than 4-acetamidobiphenyl.
- None of the tested compounds exhibited significant activity in the conversion of N-arylhydroxylamines to electrophilic intermediates, showing less than 4% of the prototype N-hydroxy-4-acetamidobiphenyl.
Conclusions:
- The presence of an ortho-hydroxyl group on the aryl ring or an alpha-hydroxyl group on the acyl moiety is insufficient to confer significant acyltransferase activity with AHAT.
- These findings clarify the structural requirements for AHAT substrate recognition and activity.
- The study highlights that specific structural features beyond simple hydroxyl group presence are critical for AHAT enzyme function.