Prolyl endopeptidase

Prolyl endopeptidase (PREP) or prolyl oligopeptidase, sometimes post-proline cleaving enzyme) is a large cytosolic enzyme that belongs to a distinct class of serine peptidases. The enzyme is involved in the maturation and degradation of peptide hormones and neuropeptides such as alpha-melanocyte-stimulating hormone, luteinizing hormone-releasing hormone (LH-RH), thyrotropin-releasing hormone; neurotensin, oxytocin, substance P and vasopressin. PREP cleaves peptide bonds at the C-terminal side of proline residues. Its activity is confined to action on oligopeptides of less than 10 kD and it has an absolute requirement for the trans-configuration of the peptide bond preceding proline.

There's an indication that altered PREP activity is associated with autism spectrum disorders and various psychological diseases such as schizophrenia, mania and clinical depression.

Some types of prolyl endopeptidase have been used in studies to decrease the propensity of gluten-containing wheat products to aggravate coeliac disease.