PREP (Prolyl Endopeptidase): PREP is an enzyme that indicates the activity of a serine protease responsible for breaking down proline-containing peptides. It plays a crucial role in the metabolism of neuropeptides and peptide hormones, contributing to cognitive processes and the inflammatory response. Variations in PREP activity have been linked to neurological disorders, including Alzheimer's disease, underscoring its significance in neurodegeneration and cognitive function.