The first mechanism-based inactivators for angiotensin-converting enzyme

Area of Science:

• Biochemistry
• Enzyme kinetics
• Medicinal chemistry

Background:

• Angiotensin-converting enzyme (ACE) plays a critical role in the renin-angiotensin system.
• ACE inhibitors are vital therapeutic agents for managing hypertension and heart failure.
• Understanding enzyme inhibition mechanisms is key to developing more effective drugs.

Purpose of the Study:

• To describe the first example of mechanism-based inactivation of ACE.
• To elucidate the mechanism by which compound 1 inactivates ACE.
• To identify key structural features responsible for ACE inhibition.

Main Methods:

• Enzyme kinetics assays to determine inhibition constants and partition ratios.
• Chemical synthesis of N-[N-(cyanoacetyl)-L-phenylalanyl]-L-phenylalanine (compound 1) and its keto analogue (compound 4).
• Proposed mechanism involving ACE-mediated deprotonation and ketenimine intermediate formation.

Main Results:

• Compound 1 demonstrated mechanism-based inactivation of ACE.
• A partition ratio (kcat/kinact) of 8300 was determined for the inactivation of ACE by compound 1.
• The keto analogue (compound 4) did not inactivate ACE, highlighting the importance of the NH group in compound 1.

Conclusions:

• N-[N-(cyanoacetyl)-L-phenylalanyl]-L-phenylalanine (compound 1) is the first described mechanism-based inhibitor of ACE.
• The NH group in compound 1 is critical for active-site anchoring and subsequent inactivation.
• The proposed mechanism involves a ketenimine intermediate that irreversibly modifies ACE, offering insights for novel ACE inhibitor design.