PAI1, or Serpin peptidase inhibitor, clade E (nexin, plasminogen activator inhibitor type 1), member 1, is a human gene encoded by SERPINE1. It may also be known as: Plasminogen activator inhibitor 1; PAI-1; Endothelial plasminogen activator inhibitor; Serpin E1; PAI; plasminogen activator inhibitor, type I; PLANH1. The encoded protein has an amino acid length of 402 and a mass of 45.1 kDa. PAI1 is a member of the Serpin family. Homologs of this gene exist in other organisms, including: Mouse, Rat, Arabidopsis, Zebrafish.