p-Guanidinobenzoic Acid Esters of Fluorescein as Active-Site Titrants of Serine Proteases

Article abstract of DOI:10.1021/ja00389a065

Two active-site titrants of serine proteases, fluorescein mono-p-guanidinobenzoate hydrochloride (FMGB*HCl) and fluorescein di-p-guanidinobenzoate dihydrochloride (FDGB*2HCl), have been synthesized, purified, and chemically and enzymatically characterized.Electronic absorbtion and fluorescence emission spectra, fluorescence lifetimes and quantum yields, solubilities, and rates of spontaneous hydrolysis at pH 7-10 are reported.Macroscopic and microscopic kinetic constants for interaction of FMGB*HCl with trypsin, urokinase, plasmin, and trombin have been determined.FMGB*HCl, which rapidly releases fluorescein upon formation of a stable acyl-enzyme intermediate with tripsin and other trypsin-like enzymes, is the most sensitive active-site titrant for serine proteases yet described.