Kinetics and Mechanism Study of Competitive Inhibition of Jack-Bean Urease by Baicalin
(a) Thiol influence on urease inactivation by BA relative to the control activity. The percent of the enzyme activity in the presence of BA without the thiol is given as comparison. Concentration of the thiol: L-cys, GSH, DTT, and BA were 3.75 mM. Enzyme activity was determined after 5, 10, 20, and 40 min of incubation. (b) Influence of thiol order of components preincubation on urease inactivation by BA. The initial 20 min preincubation mixture contained components given in brackets. The preincubation was continued the further 20 min after addition of the last component (component given outside for brackets). The final preincubation mixtures contained 0.25 mg/mL urease, 20 mM phosphate buffer, pH 7.0, 2 mM EDTA, 3.75 mM BA, and DTT, GSH, or L-cys. Enzyme activity was determined after 40 (20 + 20) min of preincubation time. The percent of the enzyme activity in the presence of BA without the thiol is given for comparison. The results are expressed as means ± SD of the data from triplicate tests.
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