Based on the provided abstracts, there is insufficient information to write a comprehensive gene function summary for PREP (prolyl endopeptidase). The abstracts primarily focus on HIV pre-exposure prophylaxis (PrEP) rather than the PREP gene/protein. Only one abstract provides relevant information about the PREP protein: it demonstrates involvement in human spermatogenesis, where PREP is engaged in microtubule-associated processes and cytoskeletal dynamics necessary for correct testis development 1. The study found that PREP expression and localization were impaired in testicular tissue and spermatozoa from infertile men, particularly in the flagellar regions, compared to normospermic men 1. This suggests PREP may serve as a potential fertility marker. However, the provided abstracts lack sufficient detail about PREP's primary enzymatic function, specific mechanisms of action, broader disease relevance beyond male fertility, or clinical significance. Additional literature focusing specifically on prolyl endopeptidase would be needed to provide a complete gene function summary covering the protein's serine-type peptidase activity and its role in cleaving peptide bonds C-terminal to proline residues.