PREP (Prolyl Endopeptidase): PREP is an enzyme that indicates the activity of a serine protease involved in the breakdown of proline-containing peptides. It plays a key 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, emphasising its role in neurodegeneration and cognitive function.