Quantitative structure-activity relationship (QSAR) study of elastase substrates and inhibitors

Area of Science:

• Biochemistry
• Enzyme kinetics
• Medicinal chemistry

Background:

• Porcine pancreatic elastase is a key enzyme in various physiological processes.
• Understanding enzyme-substrate interactions is crucial for drug design.
• Quantitative structure-activity relationships (QSAR) provide insights into molecular interactions.

Purpose of the Study:

• To synthesize and characterize peptide substrates and inhibitors for porcine pancreatic elastase.
• To quantitatively analyze the structure-activity relationships of these peptides.
• To establish a predictive model for enzyme-inhibitor interactions.

Main Methods:

• Synthesis of 100 succinyl-X-Y-aminanilide peptides and 19 trifluoroacetylated peptide inhibitors.
• Determination of kinetic parameters (Km, kcat, kcat/Km) for substrates and inhibition constants (Ki) for inhibitors.
• Quantitative analysis using the Free-Wilson/Fujita-Ban method and free-energy-related substituent constants.

Main Results:

• The contributions of amino acid side chains to kinetic constants (Km, kcat, kcat/Km) were found to be additive.
• A strong correlation was observed between inhibitor constants (Ki) and substrate Michaelis constants (Km).
• The equation log(1/Ki) = 1.271 log(1/Km) + 4.831 was validated, confirming the predictive model.

Conclusions:

• The additive nature of amino acid side chain contributions simplifies the prediction of enzyme-substrate and enzyme-inhibitor interactions.
• This study provides a foundational approach for unraveling structure-activity relationships in peptide-based therapeutics and agrochemicals.
• The validated quantitative model can guide the rational design of novel enzyme inhibitors and substrates.