Rat mast cell tryptase.
Rat mast cell tryptase is located largely if not totally in the cell's secretory granules. When the active site reagent [3H]diisopropyl fluorophosphate was used to label tryptase and chymase simultaneously, the ratio of tryptase:chymase active sites was determined to be 0.05. In comparison to chymase and tryptase in other species and chymase in the rat, rat tryptase is poorly bound to the granule matrix as evidenced by (1) its release parallel to histamine on induction of secretion and (2) its appearance in the supernatant when isolated granules were stripped of their membranes with hypotonic medium. Tryptase on release from the granule is moderately stable at a pH of 5.0 but unstable at pH 7.5, the pH that the enzyme encounters on secretion from the cell. These several properties indicate that the role of rat mast cell tryptase extracellularly is likely to differ greatly from that of chymase.
Lagunoff
D
D
Department of Pathology, St. Louis University School of Medicine, Missouri 63104.
Rickard
A
A
Marquardt
C
C
D000818:Animals; D001665:Binding Sites; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D008297:Male; D008407:Mast Cells / Q000201:enzymology*; D010447:Peptide Hydrolases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012995:Solubility
D010447:Peptide Hydrolases; C023073:tosylarginine methyl ester hydrolase