Peptidic mechanism-based inactivators for carboxypeptidase A

Area of Science:

• Biochemistry
• Enzyme kinetics
• Medicinal chemistry

Background:

• Carboxypeptidase A (CPA) is a zinc metalloprotease involved in various physiological processes.
• Mechanism-based inactivators (suicide substrates) offer a targeted approach to enzyme inhibition.
• Understanding CPA's active site is crucial for designing specific inhibitors.

Purpose of the Study:

• To investigate N-(cyanoacetyl)-L-phenylalanine and N-(3-chloropropionyl)-L-phenylalanine as the first peptidic mechanism-based inactivators for CPA.
• To elucidate the mechanism of CPA inactivation by these novel peptide substrates.
• To characterize the kinetic parameters associated with inactivation and hydrolysis.

Main Methods:

• Synthesis and kinetic evaluation of N-(cyanoacetyl)-L-phenylalanine (compound 1) and N-(3-chloropropionyl)-L-phenylalanine (compound 2).
• Determination of partition ratios for inactivation versus hydrolysis.
• Investigation of N-Acrolyl-L-phenylalanine (compound 4) as a putative intermediate and measurement of solvent deuterium isotope effects.

Main Results:

• Compounds 1 and 2 function as effective mechanism-based inactivators of CPA.
• Partition ratios of 1180 ± 40 for compound 1 and 1680 ± 60 for compound 2 were determined.
• N-Acrolyl-L-phenylalanine was confirmed as an active site-directed inactivator, and solvent deuterium isotope effects supported a promoted water hydrolytic pathway.

Conclusions:

• The studied compounds represent a novel class of peptidic suicide substrates for CPA.
• The proposed mechanism involves the formation of reactive intermediates that covalently modify the enzyme's active site.
• These findings provide insights into CPA's catalytic mechanism and pave the way for developing targeted CPA inhibitors.