scholarly journals The Catalytic Function of Nonheme Iron (III) Complex for Hydrocarbon Oxidation

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Giorgos Bilis ◽  
Maria Louloudi
Keyword(s):  
Mechanistic Model ◽  
Catalytic Efficiency ◽  
Reaction Rates ◽  
Nonheme Iron ◽  
Oxidation Products ◽  
Hydrocarbon Oxidation ◽  
Catalytic Function ◽  
Hydrocarbon Oxidations ◽  
Role Of Solvent

A detailed catalytic study of (where --[2-(3-hydroxy-1,3-diphenyl-allylideneamino)-ethylamino]--1,3-diphenyl-propen-1-ol) for hydrocarbon oxidation was carried out, focusing on the role of solvent, atmospheric dioxygen, and oxidant on catalytic efficiency. The data showed that catalyst was efficient in homogeneous hydrocarbon oxidations providing significant yields. Moreover,tert-BuOOH provided comparable oxidation yields with , slightly favoring the formation of alcohols and ketonesversusepoxides. Dioxygen intervened in the catalytic reaction, influencing the nature of oxidation products. The polarity of solvent strongly influenced the reaction rates and the nature of oxidation products. A mechanistic model is postulated assuming that functionsviathe formation of iron-hydroperoxo-species, followed by a radical-based mechanistic path.

Role of the N-terminus in human 4-hydroxyphenylpyruvate dioxygenase activity

2019 ◽  
Vol 167 (3) ◽  
pp. 315-322
Author(s):  
An-Ning Feng ◽  
Chih-Wei Huang ◽  
Chi-Huei Lin ◽  
Yung-Lung Chang ◽  
Meng-Yuan Ni ◽  
...  
Keyword(s):  
Active Site ◽  
Catalytic Efficiency ◽  
Dynamics Simulation ◽  
Wild Type ◽  
Catalytic Function ◽  
C Terminus ◽  
N Terminus ◽  
Key Enzyme ◽  
The Stability

Abstract 4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a key enzyme in tyrosine catabolism, catalysing the oxidation of 4-hydroxyphenylpyruvate to homogentisate. Genetic deficiency of this enzyme causes type III tyrosinaemia. The enzyme comprises two barrel-shaped domains formed by the N- and C-termini, with the active site located in the C-terminus. This study investigated the role of the N-terminus, located at the domain interface, in HPPD activity. We observed that the kcat/Km decreased ∼8-fold compared with wild type upon removal of the 12 N-terminal residues (ΔR13). Interestingly, the wild-type level of activity was retained in a mutant missing the 17 N-terminal residues, with a kcat/Km 11-fold higher than that of the ΔR13 mutant; however, the structural stability of this mutant was lower than that of wild type. A 2-fold decrease in catalytic efficiency was observed for the K10A and E12A mutants, indicating synergism between these residues in the enzyme catalytic function. A molecular dynamics simulation showed large RMS fluctuations in ΔR13 suggesting that conformational flexibility at the domain interface leads to lower activity in this mutant. These results demonstrate that the N-terminus maintains the stability of the domain interface to allow for catalysis at the active site of HPPD.

scholarly journals Significant role of Asn-247 and Arg-64 residues in close proximity of the active site in maintaining the catalytic function of CTX-M-15 type β-lactamase

RSC Advances ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 5325-5337 ◽  
Author(s):  
Lubna Maryam ◽  
Shamsi Khalid ◽  
Abid Ali ◽  
Asad U. Khan
Keyword(s):  
Amino Acid ◽  
Significant Role ◽  
Active Site ◽  
Catalytic Efficiency ◽  
Beta Lactamase ◽  
Amino Acid Residues ◽  
Catalytic Function ◽  
Close Proximity

Mutations of amino acid residues present near active site decrease the catalytic efficiency of beta lactamase enzymes.

Contribution of the 60 Loop To Substrate and Inhibitor Specificity of Thrombin.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1734-1734 ◽  
Author(s):  
Alireza R. Rezaie
Keyword(s):  
Active Site ◽  
Protein C ◽  
Activated Protein C ◽  
Catalytic Efficiency ◽  
Inhibitor Specificity ◽  
Active Site Pocket ◽  
Catalytic Function ◽  
Target Molecules

Relative to chymotrypsin, the 60-loop of thrombin contains 8–9 insertion residues which are believed to be partly responsible for the restricted substrate and inhibitor specificity of thrombin. Previous deletion of 3–4 residues of this loop (des-PPW and des-YPPW) dramatically impaired the activity of thrombin toward antithrombin, protein C and fibrinogen, implicating a key role for the productive interaction of these residues with the target macromolecules. To further investigate the role of this loop, we expressed a mutant of thrombin in which all 8 insertion residues (Tyr-Pro-Pro-Trp-Asp-Lys-Asn-Phe) of the 60-loop were deleted (des-60-loop). In contrast to the partially deleted loop mutants, we discovered that des-60-loop thrombin cleaved small synthetic substrates, clotted purified fibrinogen, and activated protein C with a near normal catalytic efficiency; however, its activity toward cofactors V and VIII was impaired ~2–4-fold. Further studies revealed that the reactivity of des-60-loop with antithrombin is not impaired, but rather improved ~2-fold. Remarkably, the mutant could also activate prothrombin to thrombin. These results suggest that the 60-loop plays a key role in regulating the specificity of thrombin by shielding the active-site pocket; however, its productive interaction with the target molecules may not be as critical for the catalytic function of thrombin as has been speculated in previous reports.

Designing Experiments for Model Identification of the Nitrification Process

1991 ◽  
Vol 24 (6) ◽  
pp. 9-16 ◽  
Author(s):  
P. J. Ossenbruggen ◽  
H. Spanjers ◽  
H. Aspegren ◽  
A. Klapwijk
Keyword(s):  
Mechanistic Model ◽  
Nonlinear Differential Equations ◽  
Model Identification ◽  
Reaction Rates ◽  
Variable Coefficients ◽  
Model Specification ◽  
First Order ◽  
Interactive Behavior ◽  
Batch Tests ◽  
Nitrification Process

A series of batch tests were performed to study the competition for oxygen by Nitrosomonas and Nitrobacter in the nitrification of ammonia in activated sludge. Oxygen uptake rate (OUR) and dynamic (compartment) models describing the process are proposed and tested. The OUR model is described by a Monod relationship and the biogradation process by a set of first order nonlinear differential equations with variable coefficients. The results show a mechanistic model and ten reaction rates are sufficient to capture the interactive behavior of the nitrification process. Methods for model specification, calibrating, and testing the model and the design of additional experiments are described.

scholarly journals Dye-Surfactant Interaction: Role of Solvent

2013 ◽  
Vol 25 (18) ◽  
pp. 10499-10503 ◽  
Author(s):  
Ziya Ahmad Khan ◽  
Abdullah S. Al-Bogami
Keyword(s):  
Role Of Solvent

scholarly journals Association of the OPRM1 A118G polymorphism and Pavlovian-to-instrumental transfer: Clinical relevance for alcohol dependence

2021 ◽  
pp. 026988112199199 ◽  
Author(s):  
Miriam Sebold ◽  
Maria Garbusow ◽  
Deniz Cerci ◽  
Ke Chen ◽  
Christian Sommer ◽  
...  
Keyword(s):  
Alcohol Dependence ◽  
Opioid Receptor ◽  
Mechanistic Model ◽  
Critical Role ◽  
Opioid System ◽  
Operant Behaviour ◽  
Oprm1 Gene ◽  
Potential Biomarker ◽  
A118g Polymorphism

Background: Pavlovian-to-instrumental transfer (PIT) quantifies the extent to which a stimulus that has been associated with reward or punishment alters operant behaviour. In alcohol dependence (AD), the PIT effect serves as a paradigmatic model of cue-induced relapse. Preclinical studies have suggested a critical role of the opioid system in modulating Pavlovian–instrumental interactions. The A118G polymorphism of the OPRM1 gene affects opioid receptor availability and function. Furthermore, this polymorphism interacts with cue-induced approach behaviour and is a potential biomarker for pharmacological treatment response in AD. In this study, we tested whether the OPRM1 polymorphism is associated with the PIT effect and relapse in AD. Methods: Using a PIT task, we examined three independent samples: young healthy subjects ( N = 161), detoxified alcohol-dependent patients ( N = 186) and age-matched healthy controls ( N = 105). We used data from a larger study designed to assess the role of learning mechanisms in the development and maintenance of AD. Subjects were genotyped for the A118G (rs1799971) polymorphism of the OPRM1 gene. Relapse was assessed after three months. Results: In all three samples, participants with the minor OPRM1 G-Allele (G+ carriers) showed increased expression of the PIT effect in the absence of learning differences. Relapse was not associated with the OPRM1 polymorphism. Instead, G+ carriers displaying increased PIT effects were particularly prone to relapse. Conclusion: These results support a role for the opioid system in incentive salience motivation. Furthermore, they inform a mechanistic model of aberrant salience processing and are in line with the pharmacological potential of opioid receptor targets in the treatment of AD.

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