The conversion of plasminogen proactivator to plasminogen activator by Hageman factor fragments results in the generation of chemotactic activity for human neutrophils. This chemotactic activity can be distinguished from that generated by Hageman factor activation of prekallikrein and is demonstrable in plasma that is genetically deficient in prekallikrein (Fletcher factor deficiency). Both the plasminogen-activating activity and chemotactic activity produced by the interaction of Hageman factor fragments and plasminogen proactivator to yield plasminogen activator were inhibited by diisopropyl fluorophosphate (DFP) indicating an essential role for the enzymatic site in both these activities. The finding that the plasminogen proactivator tolerated a dose of DFP, which completely inactivated the plasminogen activator, reveals that the active site is protected in the precursor protein.
Allen P. Kaplan, Edward J. Goetzl, K. Frank Austen