title: Human mast cell tryptase activates single-chain urinary-type plasminogen activator (pro-urokinase).
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.
authors.affiliation: Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: M S
authors.initials: MS
authors.lastname: Stack
authors.forename: D A
authors.initials: DA
authors.lastname: Johnson
mesh_terms: D000595:Amino Acid Sequence; D053818:Chymases; D004789:Enzyme Activation; D006801:Humans; D007532:Isoleucine; D007700:Kinetics; D008168:Lung / Q000201:enzymology*; D008239:Lysine; D008407:Mast Cells / Q000201:enzymology; D008969:Molecular Sequence Data; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D053802:Tryptases; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D007532:Isoleucine; D012697:Serine Endopeptidases; C083294:chymase 2; D053818:Chymases; D053802:Tryptases; D014568:Urokinase-Type Plasminogen Activator; D008239:Lysine; C067551:saruplase