PH-DEPENDENCE OF BOVINE MAST-CELL TRYPTASE CATALYTIC ACTIVITY AND OF ITS INHIBITION BY 4',6-DIAMIDINO-2-PHENYLINDOLE

Tryptases are oligomeric enzymes localized in the secretory granules o f mast cells. Their role(s) in vivo has yet to be clarified and the la ck of powerful and specific inhibitors has hampered the comprehension of the biological functions of these enzymes. In this paper, we identi fy 4',6-diamidino-2-phenylindole as a potent inhibitor for bovine tryp tase. This inhibitory effect and the enzyme catalyzed hydrolysis of th e synthetic substrate Boc-Phe-Ser-Arg-methyl-coumarin were investigate d in the pH range of 6.0-9.0. On the basis of the pK shifts occurring upon formation of the inhibitor(substrate)/enzyme complexes, some amin oacidic groups are proposed to play a role in such interactions. (C) 1 997 Federation of European Biochemical Societies.