Pyroglutamyl-peptidase I, also known as aminopeptidase A, is an enzyme that catalyzes the cleavage of a pyroglutamic acid (N-terminal glutamate) residue from peptides and proteins, specifically at the amino terminus of its substrates. This enzymatic activity plays a role in various physiological processes, including blood pressure regulation through the conversion of angiotensin II to angiotensin III.