ON THE REACTION OF ACETAMIDOMETHANOL WITH NATIVE AND REDUCED BOVINE PANCREATIC TRYPSIN INHIBITOR (KUNITZ INHIBITOR)

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Abstract
The stability of native and reduced bovine pancreatic trypsin inhibitor (Kunitz inhibitor) in anhydrous hydrogen fluoride and their reaction with acetamidomethanol, in the same solvent, have been investigated. The bovine Kunitz inhibitor appears to be stable in liquid hydrogen fluoride but the reduced molecule loses about 50% of its ability to regain inhibitory power, upon air oxidation, by exposure to this solvent. Tyrosine residues appear to be affected by acetamidomethylation of the native protein to give a modified inhibitor which is still highly active in inhibiting trypsin. The extent of correct refolding, upon reoxidation, of the reduced tyrosine modified-inhibitor is greatly diminished. Tyrosine modification can be prevented by carrying out the acetamidomethylation reaction in the presence of excess anisole. The stability constants and the standard free energies of binding of the complexes between trypsin and the native and the tyrosine modified-inhibitor have been determined.