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A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
Published on: September 25, 2017
Inhibition of trypsin with active-site-directed enzyme-activated nitrosoamide substrates
1Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Biochemistry
|November 21, 1995
Summary
New nitrosoamide inhibitors target trypsin
Area of Science:
- Biochemistry
- Enzyme Inhibitors
- Organic Chemistry
Background:
- Enzyme inhibitors are crucial for understanding enzyme mechanisms and developing therapeutics.
- Trypsin is a key serine protease involved in various physiological processes.
- Developing specific and efficient enzyme inhibitors remains a significant challenge in biochemistry.
Purpose of the Study:
- To design, synthesize, and evaluate novel active-site-directed enzyme-activated nitrosoamide inhibitors of trypsin.
- To investigate the mechanism of inhibition and structure-activity relationships.
- To identify potent inhibitors with potential applications as enzyme titrants.
Main Methods:
- Synthesis of a series of N-nitrosoamide compounds with varying aliphatic chain lengths.
- Enzyme inhibition assays to determine inhibition constants (k2/kinact) and half-lives.
- Competitive inhibition studies using benzamidine to confirm active site binding.
- NMR spectroscopy (13C NMR) to elucidate the mechanism of acyl migration and product formation.
Main Results:
- Several nitrosoamide compounds demonstrated potent inhibition of trypsin with half-lives of 0.6 to 2 minutes.
- Compound 1b, N-(4-amino-1-butyl)-N-nitrosobenzamide, exhibited a partition ratio of zero, indicating its potential as a trypsin titrant.
- Inhibition was confirmed to occur at the active site, as evidenced by competitive inhibition with benzamidine.
- Two inhibition modes, reversible and irreversible, were observed, with irreversible inhibition resulting from O-->N acyl migration.
Conclusions:
- N-nitrosoamide inhibitors are effective and specific for trypsin.
- The mechanism involves enzyme acylation followed by potential rearrangement to irreversible inhibition.
- Factors such as alkyl chain length, acyl-enzyme stability, acyl migration, and chirality influence inhibition modes.
- Compound 1b shows promise as a valuable tool for trypsin quantification and research.
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