[Interaction between alpha-2 macroglobulin and trypsin with synthetic trypsin inhibitors]

Area of Science:

• Biochemistry
• Enzymology

Context:

• Trypsin (Tn) forms a complex with alpha 2 Macroglobulin (alpha 2 M).
• This complex retains the hydrolytic activity of trypsin for synthetic substrates.
• Low molecular weight synthetic inhibitors can still inhibit this activity.

Purpose:

• To comparatively study the behavior of three inhibitors (Benzylamine, Butylamine, Benzamidine) with the trypsin-alpha 2 M complex.
• To investigate the effect of alpha 2 M on the enzyme-inhibitor complex dissociation constant (Ki).

Summary:

• Inhibitors bind to trypsin even when it's complexed with alpha 2 M, and alpha 2 M can bind to the trypsin-inhibitor complex.
• Alpha 2 M significantly increases the dissociation constant (Ki) for Benzamidine and Butylamine, indicating altered inhibitor binding affinity.
• This increase in Ki is attributed to structural modifications in alpha 2 M upon complex formation, affecting inhibitor accessibility to the active site.

Impact:

• The study reveals that alpha 2 M undergoes irreversible structural changes during complex formation.
• These structural changes influence inhibitor binding kinetics, increasing the dissociation constant (Ki).
• The findings suggest that while inhibitor binding is affected, the overall association constant of the trypsin-alpha 2 M complex is not effectively decreased.