title: A fluorogenic active-site titrant for serine proteases.
abstract: The synthesis of 3'-(4-guanidinobenzoyloxy)-spiro(isobenzofuran-1(3H),9H-[9H]xan then]-3-one or 3HFGB, an active-site titrant for serine proteases, is described. 3HFGB has two advantages over previously described titrants. It is very sensitive (it can measure serine proteases at the 10(-11)-10(-12) M level), and it can be used at stoichiometric ratios of titrant to protease of unity or less. Moreover, the fluorogenic leaving group, 3'-hydroxyspiro[isobenzofuran-1(3H),9'-[9H]xanthen]-3- one, is suitable for use in a range of esteropeptidase substrates. The use of 3HFGB in the active-site titration of trypsin is described.
mesh_terms: D001665:Binding Sites; D010450:Endopeptidases / Q000032:analysis*; D005453:Fluorescence; D006146:Guanidines; D012697:Serine Endopeptidases; D014970:Xanthines
chemical_list: D006146:Guanidines; D014970:Xanthines; C045388:3'-(4-guanidinobenzoyloxy)spiro(isobenzofuran-1-(3H),9'-(9H)xanthen)-3-one; D010450:Endopeptidases; D012697:Serine Endopeptidases