Kinetics of the course of inactivation of aminoacylase by 1,10-phenanthroline.
The kinetic theory of the substrate reaction during modification of enzyme activity previously described [Tsou (1988) Adv. Enzymol. Relat. Areas Mol. Biol. 61, 381-436] has been applied to a study on the kinetics of the course of inactivation of aminoacylase by 1,10-phenanthroline. Upon dilution of the enzyme that had been incubated with 1,10-phenanthroline into the reaction mixture, the activity of the inhibited enzyme gradually increased, indicating dissociation of a reversible enzyme--1,10-phenanthroline complex. The kinetics of the substrate reaction with different concentrations of the substrate chloroacetyl-L-alanine and the inactivator suggest a complexing mechanism for inactivation by, and substrate competition with, 1,10-phenanthroline at the active site. The inactivation kinetics are single phasic, showing that the initial formation of an enzyme-Zn(2+)-1,10-phenanthroline complex is a relatively rapid reaction, followed by a slow inactivation step that probably involves a conformational change of the enzyme. The presence of Zn2+ apparently stabilizes an active-site conformation required for enzyme activity.
Wang
Z X
ZX
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, People's Republic of China.
Wu
H B
HB
Wang
X C
XC
Zhou
H M
HM
Tsou
C L
CL
D000581:Amidohydrolases / Q000037:antagonists & inhibitors*; D000818:Animals; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D010618:Phenanthrolines / Q000494:pharmacology*; D013552:Swine; D015032:Zinc / Q000494:pharmacology
D010618:Phenanthrolines; D000581:Amidohydrolases; C019672:aminoacylase I; D015032:Zinc; C025205:1,10-phenanthroline