scholarly journals Kinetics and Mechanism Study of Competitive Inhibition of Jack-Bean Urease by Baicalin

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Lirong Tan ◽  
Jiyan Su ◽  
Dianwei Wu ◽  
Xiaodan Yu ◽  
Zuqing Su ◽  
...  
Keyword(s):  
Active Site ◽  
Competitive Inhibition ◽  
Therapeutic Potential ◽  
Sulfhydryl Group ◽  
Principal Component ◽  
Kinetics And Mechanism ◽  
Inhibition Constant ◽  
Jack Bean Urease ◽  
Mechanism Study ◽  
Jack Bean

Baicalin (BA) is the principal component of Radix Scutellariae responsible for its pharmacological activity. In this study, kinetics and mechanism of inhibition by BA against jack-bean urease were investigated for its therapeutic potential. It was revealed that the IC50of BA against jack-bean urease was2.74 ± 0.51 mM, which was proved to be a competitive and concentration-dependent inhibition with slow-binding progress curves. The rapid formation of initial BA-urease complex with an inhibition constant ofKi=3.89 × 10−3 mM was followed by a slow isomerization into the final complex with an overall inhibition constant ofKi*=1.47×10-4 mM. High effectiveness of thiol protectors against BA inhibition indicated that the strategic role of the active-site sulfhydryl group of the urease was involved in the blocking process. Moreover, the inhibition of BA was proved to be reversible due to the fact that urease could be reactivated by dithiothreitol but not reactant dilution. Molecular docking assay suggested that BA made contacts with the important activating sulfhydryl group Cys-592 residues and restricted the mobility of the active-site flap. Taken together, it could be deduced that BA was a competitive inhibitor targeting thiol groups of urease in a slow-binding manner both reversibly and concentration-dependently, serving as a promising urease inhibitor for treatments on urease-related diseases.

Jack bean urease (EC 3.5.1.5). IV. The molecular size and the mechanism of inhibition by hydroxamic acids. Spectrophotometric titration of enzymes with reversible inhibitors

1980 ◽  
Vol 58 (12) ◽  
pp. 1323-1334 ◽  
Author(s):  
Nicholas E. Dixon ◽  
John A. Hinds ◽  
Ann K. Fihelly ◽  
Carlo Gazzola ◽  
Donald J. Winzor ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Active Site ◽  
Binding Sites ◽  
Spectrophotometric Titration ◽  
Hydroxamic Acids ◽  
Jack Bean Urease ◽  
Equivalent Weight ◽  
Guanidinium Chloride ◽  
Jack Bean ◽  
Equilibrium Ultracentrifugation

Kinetic, spectral, and other studies establish that hydroxamic acids bind reversibly to active-site nickel ion in jack bean urease. Equilibrium ultracentrifugation studies establish that the molecular weight of native urease is 590 000 ± 30 000 while that of the subunit formed in 6 M guanidinium chloride in the presence of β-mercaptoethanol is ~95 000. Essentially the same subunit molecular weight (~93 000) is found by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, subsequent to denaturation in a guanidinium chloride – β-mercaptoethanol system at various temperatures. Coupled with an equivalent weight of 96 600 for binding of the inhibitors acetohydroxamic acid and phosphoramidate, these results establish securely that urease is a hexamer with one active site per 96 600-dalton subunit. Consistent values for the equivalent weight are obtained by a routine spectrophotometric titration of the active site of freshly prepared urease with trans-cinnamoylhydroxamic acid. General equations are derived which describe spectrophotometric titrations of binding sites of any enzyme with a reversible inhibitor. These equations allow the evaluation of the difference spectrum of the protein–inhibitor complex even when the binding sites cannot readily be saturated with the inhibitor or vice versa.

Synthesis, cytotoxic and urease inhibitory activities of some novel isatin-derived bis-Schiff bases and their copper(ii) complexes

MedChemComm ◽  
2016 ◽  
Vol 7 (5) ◽  
pp. 914-923 ◽  
Author(s):  
Humayun Pervez ◽  
Maqbool Ahmad ◽  
Sumera Zaib ◽  
Muhammad Yaqub ◽  
Muhammad Moazzam Naseer ◽  
...  
Keyword(s):  
Schiff Bases ◽  
Active Compound ◽  
Active Site ◽  
Binding Mode ◽  
Jack Bean Urease ◽  
Jack Bean ◽  
Inhibitory Activities ◽  
Urease Inhibitory

The putative binding mode of the most active compound 3b in the active site of Jack bean urease.

scholarly journals Kinetics and mechanism of jack bean urease inhibition by Hg2+

2012 ◽  
Vol 6 (1) ◽  
Author(s):  
Nana Du ◽  
Mingming Chen ◽  
Zhaodi Liu ◽  
Liangquan Sheng ◽  
Huajie Xu ◽  
...  
Keyword(s):  
Kinetics And Mechanism ◽  
Urease Inhibition ◽  
Jack Bean Urease ◽  
Jack Bean

Jack bean urease (EC 3.5.1.5). V. On the mechanism of action of urease on urea, formamide, acetamide, N-methylurea, and related compounds

1980 ◽  
Vol 58 (12) ◽  
pp. 1335-1344 ◽  
Author(s):  
Nicholas E. Dixon ◽  
Peter W. Riddles ◽  
Carlo Gazzola ◽  
Robert L. Blakeley ◽  
Burt Zerner
Keyword(s):  
Enzymatic Hydrolysis ◽  
Mechanism Of Action ◽  
Active Site ◽  
Ph Dependence ◽  
Jack Bean Urease ◽  
Nickel Ion ◽  
Jack Bean ◽  
First Time ◽  
Hydrolysis Of ◽  
Hydrolysis Of Urea

Acetamide and N-methylurea have been shown for the first time to be substrates for jack bean urease. In the enzymatic hydrolysis of urea, formamide, acetamide, and N-methylurea at pH 7.0 and 38 °C, kcat has the values 5870, 85, 0.55, and 0.075 s−1, respectively. The urease-catalyzed hydrolysis of all these substrates involves the active-site nickel ion(s). Enzymatic hydrolysis of the following compounds could not be detected: phenyl formate, p-nitroformanilide, trifluoroacetamide, p-nitrophenyl carbamate, thiourea, and O-methylisouronium ion. In the enzymatic hydrolysis of urea, the pH dependence of kcat between pH 3.4 and 7.8 indicates that at least two prototropic forms are active. Enzymatic hydrolysis of urea in the presence of methanol gave no detectable methyl carbamate. A mechanism of action for urease is proposed which involves initially an O-bonded complex between urea and an active-site Ni2+ ion and subsequently an O-bonded carbamato–enzyme intermediate.

Synthesis, biological evaluation and docking studies of some novel isatin-3-hydrazonothiazolines

RSC Advances ◽  
2016 ◽  
Vol 6 (65) ◽  
pp. 60826-60844 ◽  
Author(s):  
Maqbool Ahmad ◽  
Humayun Pervez ◽  
Sumera Zaib ◽  
Muhammad Yaqub ◽  
Muhammad Moazzam Naseer ◽  
...  
Keyword(s):  
Active Site ◽  
Binding Mode ◽  
Docking Studies ◽  
Biological Evaluation ◽  
Jack Bean Urease ◽  
Jack Bean

The putative binding mode of compound 6i in the active site of Jack bean urease.

Inactivation of jack bean urease by scutellarin: Elucidation of inhibitory efficacy, kinetics and mechanism

Fitoterapia ◽  
2013 ◽  
Vol 91 ◽  
pp. 60-67 ◽  
Author(s):  
Dian-Wei Wu ◽  
Xiao-Dan Yu ◽  
Jian-Hui Xie ◽  
Zu-Qing Su ◽  
Ji-Yan Su ◽  
...  
Keyword(s):  
Kinetics And Mechanism ◽  
Jack Bean Urease ◽  
Jack Bean

Jack bean urease (EC 3.5.1.5). III. The involvement of active-site nickel ion in inhibition by β-mercaptoethanol, phosphoramidate, and fluoride

1980 ◽  
Vol 58 (6) ◽  
pp. 481-488 ◽  
Author(s):  
Nicholas E. Dixon ◽  
Robert L. Blakeley ◽  
Burt Zerner
Keyword(s):  
Dissociation Constant ◽  
Active Site ◽  
Competitive Inhibitor ◽  
Jack Bean Urease ◽  
Nickel Ion ◽  
Nickel Ions ◽  
Jack Bean ◽  
Complex Fluoride ◽  
Spectral Changes ◽  
Hydrolysis Of

Interaction of β-mercaptoethanol with urease produces large, rapid and fully reversible spectral changes in that part of the electronic absorption spectrum which is associated with the tightly bound nickel ions. The spectrophotometrically determined value of the dissociation constant of the β-mercaptoethanol–urease complex (0.95 ± 0.05 mM at pH 7.12 and 25 °C) is in agreement with the Ki (0.72 ± 0.26 mM) for β-mercaptoethanol acting as a competitive inhibitor in the hydrolysis of urea. This constitutes direct evidence that the nickel in jack bean urease is at the active site. Inhibition of urease by phosphoramidate is slowly achieved and slowly reversed, and upon reactivation of the isolated phosphoramidate–urease complex, phosphoramidate is regenerated in good yield. Spectrophotometric experiments indicate that phosphoramidate binds to nickel ion in urease. Competition with β-mercaptoethanol was used to determine a dissociation constant (1.23 ± 0.10 mM at pH 7.12 and 25 °C) for a fluoride–urease complex in which fluoride ion also coordinates with an active-site nickel ion. Kinetic evidence is presented which indicates that in the presence of urea, a ternary complex (fluoride–urea–urease) is formed.

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