Synthesis and Structural Characterization of Macrocyclic Plasmin Inhibitors

Area of Science:

• Biochemistry
• Medicinal Chemistry
• Structural Biology

Background:

• Plasmin is a key enzyme in fibrinolysis, and its inhibitors are crucial for treating bleeding disorders.
• Developing selective inhibitors is challenging due to the structural similarity of serine proteases.

Purpose of the Study:

• To synthesize and characterize novel macrocyclic plasmin inhibitors.
• To elucidate the structural basis for their selectivity against other proteases.

Main Methods:

• Chemical synthesis of macrocyclic compounds with C-terminal benzylamine groups.
• Enzyme inhibition assays to determine inhibition constants (K_i).
• X-ray crystallography to determine inhibitor-plasmin complex structures.

Main Results:

• Two analogues achieved sub-nanomolar inhibition constants for plasmin.
• Compounds demonstrated high selectivity against other trypsin-like serine proteases.
• Crystal structures revealed inhibitor binding in the open active site, incompatible with the 99-hairpin loop of other proteases.

Conclusions:

• The novel macrocyclic inhibitors exhibit potent and selective inhibition of plasmin.
• Structural data explains the observed selectivity, paving the way for targeted therapies.
• This work provides a foundation for designing next-generation plasmin inhibitors.