A TEST FOR DIFFUSIBLE IONS : I. THE IONIC NATURE OF TRYPSIN

Area of Science:

• Biochemistry
• Physical Chemistry

Background:

• The Donnan equilibrium principle explains ion distribution across semipermeable membranes.
• Understanding the ionic nature of enzymes like trypsin is crucial for biochemical applications.

Purpose of the Study:

• To determine the ionic state and charge of trypsin using the Donnan equilibrium.
• To investigate trypsin's behavior in solution across a range of pH values.

Main Methods:

• Comparing the distribution of trypsin across gelatin particles to that of hydrogen and chloride ions.
• Utilizing the Donnan equilibrium as a method to infer ionic properties.

Main Results:

• Trypsin distribution ratios matched hydrogen ion ratios and were inversely proportional to chloride ion ratios between pH 2.0 and 10.2.
• At pH 10.2, trypsin distribution was equal; above this pH, it followed chloride ion ratios.
• Trypsin exhibited properties of a positive monovalent ion from pH 2.0 to 10.2 and a negative monovalent ion above pH 10.2.

Conclusions:

• Trypsin behaves as a positive monovalent ion in acidic to neutral solutions and a negative monovalent ion in alkaline solutions.
• Trypsin is likely isoelectric at pH 10.2 and acts as a strong base.
• These findings confirm trypsin's ionic nature and provide insights into its behavior in biological systems.