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  • Title: Human mast cell tryptase activates single-chain urinary-type plasminogen activator (pro-urokinase).
    Author: Stack MS, Johnson DA.
    Journal: J Biol Chem; 1994 Apr 01; 269(13):9416-9. PubMed ID: 8144524.
    Abstract:
    Human lung mast cell tryptase is a trypsin-like serine proteinase that is stored in mast cell granules and released by activated mast cells. Here we report that mast cell tryptase is a potent activator of single-chain urinary-type plasminogen activator (scu-PA, or prourokinase), the zymogen form of urinary-type plasminogen activator (u-PA). Activation was complete within 75 min using an enzyme:substrate molar ratio of 1:50 and was accompanied by cleavage of scu-PA at Lys158-Ile159, generating active two-chain u-PA. The reaction was dependent on enzyme concentration and obeyed Michaelis-Menten kinetics. Kinetic constants calculated for scu-PA activation by mast cell tryptase are Km = 34 microM, Vmax = 3.6 pmol of u-PA/min, and kcat = 0.08 s-1. These data suggest that tryptase from tumor-associated mast cells may participate in the activation of scu-PA.
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