title: Irreversible inactivation of human erythrocyte pyruvate kinase by 2,3-butanedione.
abstract: Human erythrocyte pyruvate kinase was found to be irreversibly inactivated by butanedione in the dark. The second-order rate constants for inactivation at pH 8.0 and 25 degrees C were 2.14 and 2.74 M-1 min-1 in the absence and presence of 50 mM borate, respectively. The pH profile of the inactivation indicated the involvement of a residue with an apparent pK alpha of 8.1-8.3. ADP and phosphoenolpyruvate acted as partial inhibitors of the inactivation process. Certain details of the inactivation, spectral studies, and fluorometric determinations gave evidence for arginine as the only target residue. A total of 23 +/- 3 residues per subunit were modified within the period required for inactivation. In the same period the presence of 4 mM ADP reduced the extent of inactivation by 70% and the number of modified residues to 18 +/- 4. The number of the arginine residues protected by ADP from butanedione modification was 5.0 +/- 1.3 per subunit.
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D001881:Borates / Q000494:pharmacology; D002074:Butanones / Q000494:pharmacology*; D003931:Diacetyl / Q000494:pharmacology*; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011770:Pyruvate Kinase / Q000037:antagonists & inhibitors* / Q000097:blood
chemical_list: D001881:Borates; D002074:Butanones; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D011770:Pyruvate Kinase; D003931:Diacetyl