Serpin Peptidase Inhibitory, clade F (SERPINF1), previously called Pigment epithelium-derived factor (PEDF), is encoded by the SERPINF1 gene in humans and found in vertebrates. It is a secreted phosphoglycoprotein that belongs to the clade F subfamily, serpin superfamily of proteinase inhibitors. SERPINF1 is a noninhibitory serpin with neurotrophic, anti-angiogenic, and anti-tumorigenic properties. It is synthesized as a 418 amino acid, ~50 kDa precursor that contains a 19 amino acid signal sequence and a 399 amino acid mature region that shows a pyroglutamate at Gln20. Like other serpins, it contains three β-sheets, 810 α-helices, and a C-terminal RCL (reactive center loop). Unlike other serpins with Ser protease inhibiting activity, SERPINF1 has induces extensive neuronal differentiation in retinoblastoma cells, inhibiting of angiogenesis. As it does not undergo the S (stressed) to R (relaxed) conformational transition characteristic of active serpins, it exhibits no serine protease inhibitory activity. SERPINF1 is researched as a therapeutic candidate for treatment of such conditions as choroidal neovascularization, heart disease, and cancer.