Limited proteolysis in porous membrane reactors containing immobilized trypsin

Area of Science:

• Biochemistry
• Analytical Chemistry
• Materials Science

Background:

• Proteolysis is essential for protein characterization using mass spectrometry.
• Limited proteolysis generates larger peptides, revealing protein flexibility and accessible regions.

Purpose of the Study:

• To explore controlled, limited proteolysis using immobilized trypsin within porous nylon membranes.
• To investigate how membrane properties and enzyme immobilization affect proteolysis outcomes.

Main Methods:

• Proteins were passed through porous nylon membranes with immobilized trypsin.
• Reaction times were controlled by membrane thickness (∼100 μm) and flow rates (milliseconds).
• Membrane pore size (e.g., 5.0 μm, 1.2 μm) and trypsin immobilization methods (electrostatic, covalent) were varied.

Main Results:

• Large pores and covalent enzyme anchoring produced long tryptic peptides from β-casein.
• Short residence times and smaller pores with electrostatic immobilization yielded large peptides from cytochrome c and apomyoglobin.
• Specific cleavages in flexible regions of cytochrome c and apomyoglobin generated two large peptides covering the entire protein sequence.

Conclusions:

• In-membrane, controlled proteolysis offers a method for generating large peptides for protein analysis.
• This technique enhances the characterization of protein structure, flexibility, and accessible regions.
• Optimizing membrane characteristics and enzyme immobilization allows precise control over limited proteolysis.