Zhao O, Kovach IM. Reversible modification of tissue-type plasminogen activator by methylphosphonate esters.
Bioorg Med Chem 1996;
4:523-9. [PMID:
8735839 DOI:
10.1016/0968-0896(96)84792-4]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In spite of their rapid aqueous hydrolysis, 4-nitrophenyl 4-X-phenacyl methylphosphonates (X = H, (PMN) CH3, CH3O, Cl and NO2) inactivate many serine proteases of the pancreatic and blood coagulation systems efficiently. The rate constants, K/Ki, for the inactivation of tissue-type plasminogen activator enzyme (t-PA) are 470-750 M-1 S-1 with PMN, 4-CH3-PMN, and 4-CH3O-PMN in pH 7.8, 0.05 M Tris buffer at 7.0 +/- 0.5 degrees C, but t-PA cannot be inhibited with the 4-Cl and NO2 derivatives due to rapid competing hydrolysis. Enzyme activity returns from each enzyme-adduct at a characteristic rate, due to a self-catalyzed intramolecular reactivation process. The rate constants for spontaneous reactivation of t-PA from the adducts formed with the three inhibitors are K = 0.25-12.3 x 10(-2) min-1 at pH 7.4 and 25.0 +/- 0.1 degrees C and pH-dependent with an apparent pK approximately 8.3. The recovery of t-PA activity from the adducts in 40% human plasma buffered at pH 7.4 is the same or twice that in plain buffer. The presence of fibrin has a slight effect on inactivation but not on reactivation. The modulation of enzyme activity by reversible generation of the phosphonylated adducts has potential for medical application.
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