Angiostatin, is a ~30 kDa fragment of plasminogen that is encoded by the PLG gene in humans. It is produced, for example, by autoproteolytic cleavage of plasminogen, involving extracellular disulfide bond reduction by phosphoglycerate kinase. Furthermore, angiostatin can be cleaved from plasminogen by different metalloproteinases (MMPs), elastase, prostate-specific antigen (PSA), 13 kDa serine protease, or 24 kDa endopeptidase. Angiostatin is known to bind many proteins, especially to angiomotin and endothelial cell surface ATP synthase but also integrins, annexin II, C-met receptor, NG2 proteoglycan, tissue-type plasminogen activator, chondroitin sulfate proteoglycans, and CD26. It seems to involve inhibition of endothelial cell migration, proliferation and induction of apoptosis, but its mechanism of action is still unclear. Angiostatin is currently undergoing clinical trials for its use in anticancer therapy. Recombinant angiostatin is expressed in E. coli.