Fig. 1.

Pathway for the generation of angiostatin from plasminogen (outlined by Geiger and Cnudde [2004]). Angiostatin is thought to be generated from plasminogen by the following steps: u-PA (urikinase plasminogen activator) or t-PA (tissue plasminogen activator) proteolytically cleaves plasminogen to generate plasmin, and a reduction of disulfide bonds (potentially by phosphoglycerate kinase [PGK]) allows a serine protease to proteolytically cleave plasmin, generating K1–4½, followed by proteolytic cleavage by MMPs to generate angiostatin (K1–4 or angiostatin K1–3).