Recombinant plasminogen activator inhibitor-1 (PAI-1) isoforms which lack the reactive center loop and contain the complete heparin-binding domain or lack at least a portion of the heparin-binding domain are described. The rPAI-1 isoforms disclosed herein may be used to modulate angiogenesis through blocking release of VEGF from a VEGF-heparin complex. Furthermore, the rPAI-1 proteins may be used to inhibit cell proliferation and migration, induce apoptosis, and produce proteolytic fragments corresponding to angiostatin kringles 1-3 and kringles 1-4. A truncated proteolytic plasmin protein of 34 kDa is also provided.