The rapid reaction of diisopropylfluorophosphate with a tyrosine residue of human serum albumin at 0.02 m ionic strength involves prior rapid reversible binding characterized by a dissociation constant of 3.6 × 10-3 m and an apparent pKa of 8.3. The rapid reaction of p-nitrophenyl acetate with human serum albumin (G. E. Means and M. L. Bender, 1975, Biochemistry 14, 4989-4994) appears to involve the same tyrosine residue and is thus stoichiometrically inhibited by prior reaction with diisopropylfluorophosphate. Both reactions are strongly inhibited by decanoate anion, strongly retarded at higher ionic strength, and reflect strong rapidly reversible binding and abnormally low tyrosine pKa values. This reactive tyrosine residue thus appears to be located in a primary binding site for small apolar anions and to be closely associated with several cationic groups.
All Science Journal Classification (ASJC) codes
- Molecular Biology