Substrate specificity of pyroglutamylaminopeptidase.

Three synthetic peptides (compounds 4-6) were tested as substrates of pyroglutamylaminopeptidase. In addition, inhibition of the hydrolysis of these substrates by compounds 8 and 9 was also examined. The enzyme does not appreciably catalyze the hydrolysis of peptides with six-membered ureido rings at the amino terminus, but it tolerates well a five-membered ureido ring at this position.