Suicide inactivation of human prostatic acid phosphatase and a phosphotyrosine phosphatase.

4-Difluoromethylphenyl bis(cyclohexylammonium) phosphate was synthesized in 4 steps starting from dibenzyl phosphite and shown to be a time-dependent suicide inactivator of human prostatic acid phosphatase and the SHP protein tyrosine phosphatase. The inactivation of human prostatic acid phosphatase followed pseudo-first-order kinetics with inactivation constants of Ki = 1.0 mM; ki = 0.15 min-1 (t1/2 = 4.6 min at saturation). Phenyl phosphate protected the enzyme against inactivation, indicating that inactivation occurs in the active site. The inactivation of SHP also followed pseudo-first-order kinetics, with a t1/2 = approximately 15 min in the presence of 8.2 mM inhibitor. The mechanism of inactivation likely involves the enzymatic release of difluoromethyl phenol which rapidly eliminates fluoride, generating a quinone methide. This potent electrophile then reacts with residues at the active site of the enzyme. This inhibitor and peptidic derivatives thereof have excellent potential for selective inactivation and labeling of protein tyrosine phosphatases.