Pigment epithelium-derived factor (PEDF), a serpin with potent anti-angiogenic and neurite outgrowth-promoting properties.

Pigment epithelium-derived factor is a member of the serpin superfamily of proteins, but one that lacks inhibitory properties against either serine or cysteine proteinases. Nevertheless it possesses a number of physiological properties that make it a potentially important protein in regulation of angiogenesis, in neuronal cell survival and in protection of neurons from neurotoxic agents. It is also a protein that is highly up-regulated in the G0 phase of early-passage cells compared with rapidly proliferating cells or senescent cells, and so is also linked to both the cell cycle and cell senescence. The determination of a high resolution X-ray crystal structure of native PEDF provides insight into regions of the protein that may be involved in one or more of these functions.