Pyroglutamyl-Peptidase I（PGPEP1) is an omega peptidase which detaches pyroglutamyl residues from the amino termini of peptides and proteins. PGPEP1 is a cytosolic cysteine peptidase which is expressed in most cell types. PGPEP1 enzyme has need of s a thiol-reducing agent for activity. PGPEP1 is possibly involved in the inactivation of biologically active peptides which have an amino terminal pyroglutamyl group， for instance peptides as neurotensin， luteinizing hormone releasing hormone， and thyrotropinreleasing hormone.
