Pyroglutamyl diazomethyl ketone: Potent inhibitor of mammalian pyroglutamyl peptide hydrolase

Pyroglutamyl peptide hydrolase (EC 3.4.11.8), a cysteine protease, cleaves the N-terminal pyroglutamyl residue from pyroglutamyl peptides such as thyrotropin releasing hormone. Pyroglutamyl diazomethyl ketone was synthesized as an active site directed inhibitor. Preincubation of the partially purified bovine brain enzyme with nanomolar concentrations of inhibitor produced rapid inactivation. Inhibitor concentrations five orders of magnitude higher did not inactivate other exo- and endopeptidases. A dose of 0.1 mg/kg administered intraperitoneally to mice totally inactivated the enzyme in all tissues studied including brain. Pyroglutamyl diazomethyl ketone should be of value in studies on the physiological role of this enzyme in the metabolism of pyroglutamyl-containing peptides.