scholarly journals The inter-dimeric interface controls function and stability ofUreaplasma urealiticummethionine S-adenosyltransferase

2019 ◽  
Author(s):  
Daniel Kleiner ◽  
Fannia Shmulevich ◽  
Raz Zarivach ◽  
Anat Shahar ◽  
Michal Sharon ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Enzymatic Activity ◽  
Active Site ◽  
Active Sites ◽  
Structural Integrity ◽  
Functional Unit ◽  
Proteolytic Degradation ◽  
Interface Area ◽  
Dimeric Interface ◽  
Product Accumulation

SummaryMethionine S-adenosyltransferases (MATs) are predominantly homotetramers, comprised of dimers of dimers. The highly conserved dimeric interface harbors two active sites, making the dimer the obligatory functional unit. Yet, functionality of the recently evolved inter-dimeric interface remains unknown. Here, we show that the inter-dimeric interface ofU. urealiticumMAT has evolved to control the catalytic activity and structural integrity of the homotetramer in response to product accumulation. When all four active sites are occupied with the product, S-adenosylmethionine (SAM), binding of four additional SAM molecules to the inter-dimeric interface prompts a ∼45° shift in the dimer orientation and a concomitant ∼60% increase in the interface area. This rearrangement inhibits the enzymatic activity by locking the flexible active site loops in a closed state and renders the tetramer resistant to proteolytic degradation. Our findings suggest that the inter-dimeric interfaces of MATs are recruited by evolution to tune the molecular properties of the entire homotetramer.

Catalytic mechanisms of oxygen-containing groups over vanadium active sites in an Al-MCM-41 framework for production of 2,5-diformylfuran from 5-hydroxymethylfurfural

2020 ◽  
Vol 10 (1) ◽  
pp. 278-290 ◽  
Author(s):  
Li-Juan Liu ◽  
Zhao-Meng Wang ◽  
Ya-Jing Lyu ◽  
Jin-Feng Zhang ◽  
Zhou Huang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Site ◽  
Active Sites ◽  
Hydroxyl Group ◽  
Catalytic Mechanisms ◽  
Mcm 41

In the V-doped Al-MCM-41 framework, the [V-1] active site with a hydroxyl group displays better catalytic activity than the [V-0] active site without a hydroxyl group toward the oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran.

scholarly journals Comparative Characterization of CTX-M-64 and CTX-M-14 Provides Insights into the Structure and Catalytic Activity of the CTX-M Class of Enzymes

2016 ◽  
Vol 60 (10) ◽  
pp. 6084-6090 ◽  
Author(s):  
Dandan He ◽  
Jiachi Chiou ◽  
Zhenling Zeng ◽  
Edward Wai-Chi Chan ◽  
Jian-Hua Liu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Amino Acid ◽  
Active Site ◽  
Structural Integrity ◽  
Amino Acid Residues ◽  
Active Site Residues ◽  
Significant Difference ◽  
Function Relationship ◽  
Alignment Analysis ◽  
M 14

ABSTRACTClinical isolates producing hybrid CTX-M β-lactamases, presumably due to recombination between theblaCTX-M-15andblaCTX-M-14elements, have emerged in recent years. Among the hybrid enzymes, CTX-M-64 and CTX-M-14 display the most significant difference in catalytic activity. This study aims to investigate the mechanisms underlying such differential enzymatic activities in order to provide insight into the structure/function relationship of this class of enzymes. Sequence alignment analysis showed that the major differences between the amino acid composition of CTX-M-64 and CTX-M-14 lie at both the N and C termini of the enzymes. Single or multiple amino acid substitutions introduced into CTX-M-64 and CTX-M-14 were found to produce only minor effects on hydrolytic functions; such a finding is consistent with the notion that the discrepancy between the functional activities of the two enzymes is not the result of only a few amino acid changes but is attributable to interactions between a unique set of amino acid residues in each enzyme. This theory is supported by the results of the thermal stability assay, which confirmed that CTX-M-64 is significantly more stable than CTX-M-14. Our data confirmed that, in addition to the important residues located in the active site, residues distal to the active site also contribute to the catalytic activity of the enzyme through stabilizing its structural integrity.

scholarly journals Insights into the role of an Fe–N active site in the oxygen reduction reaction on carbon-supported supramolecular catalysts

RSC Advances ◽  
2020 ◽  
Vol 10 (15) ◽  
pp. 8709-8716
Author(s):  
Lin Gu ◽  
Yunyun Dong ◽  
Yan Zhang ◽  
Bo Wang ◽  
Qing Yuan ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Site ◽  
Active Sites ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Supramolecular Catalysts

The PPYTZ–Fe/C catalyst containing Fe–N active sites exhibited high ORR catalytic activity and stability in alkaline media with a four-electron pathway progress.

scholarly journals A Kinetic Approach to Defining the Role of Chemically Modifiable Residues at the Active Sites of Enzymes

1975 ◽  
Vol 28 (4) ◽  
pp. 379
Author(s):  
Leonie K Ashman ◽  
D Bruce Keech
Keyword(s):  
Biological Activity ◽  
Catalytic Activity ◽  
Kinetic Analysis ◽  
Active Site ◽  
Initial Velocity ◽  
Active Sites ◽  
Kinetic Approach ◽  
Modified Enzyme ◽  
Enzyme Molecules

Initial velocity studies can be used to define the function of chemically modifiable residues in the active site of a multisubstrate enzyme. Since the method relies on measuring biological activity, it has the advantage that it can be used with small amounts of relatively impure enzyme, but requires that modified enzyme molecules have some residual catalytic activity. The kinetic analysis of the modified enzyme can be carried out in the presence of some unmodified enzyme molecules.

scholarly journals Inactivation of horse liver mitochondrial aldehyde dehydrogenase by disulfiram. Evidence that disulfiram is not an active-site-directed reagent

1987 ◽  
Vol 242 (2) ◽  
pp. 499-503 ◽  
Author(s):  
C G Sanny ◽  
H Weiner
Keyword(s):  
Catalytic Activity ◽  
Aldehyde Dehydrogenase ◽  
Active Site ◽  
Active Sites ◽  
Specific Activity ◽  
Cysteine Residue ◽  
Complete Inactivation ◽  
Horse Liver ◽  
Inactivation Mechanism ◽  
Liver Aldehyde Dehydrogenase

The inhibition of mitochondrial (pI 5) horse liver aldehyde dehydrogenase by disulfiram (tetraethylthiuram disulphide) was investigated to determine if the drug was an active-site-directed inhibitor. Stoichiometry of inhibition was determined by using an analogue, [35S]tetramethylthiuram disulphide. A 50% loss of the dehydrogenase activity was observed when only one site per tetrameric enzyme was modified, and complete inactivation was not obtained even after seven sites per tetramer were modified. Modification of only two sites accounted for a loss of 75% of the initial catalytic activity. The number of functioning active sites per tetrameric enzyme, as determined by the magnitude of the pre-steady-state burst of NADH formation, did not decrease until approx. 75% of the catalytic activity was lost. These data indicate that disulfiram does not modify the essential nucleophilic amino acid at the active site of the enzyme. The data support an inactivation mechanism involving the formation of a mixed disulphide with a non-essential cysteine residue, resulting in a lowered specific activity of the enzyme.

scholarly journals Ammonia Decomposition Enhancement by Cs-Promoted Fe/Al2O3 Catalysts

2020 ◽  
Vol 150 (12) ◽  
pp. 3369-3376
Author(s):  
Luke A. Parker ◽  
James H. Carter ◽  
Nicholas F. Dummer ◽  
Nia Richards ◽  
David J. Morgan ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Induction Period ◽  
Active Site ◽  
Active Sites ◽  
Decomposition Reaction ◽  
Ammonia Decomposition ◽  
Site Analysis ◽  
Rate Determining Step ◽  
Equilibrium Conversion ◽  
On Line

Abstract A range of Cs-doped Fe/Al2O3 catalysts were prepared for the ammonia decomposition reaction. Through time on-line studies it was shown that at all loadings of Cs investigated the activity of the Fe/Al2O3 catalysts was enhanced, with the optimum Cs:Fe being ca. 1. Initially, the rate of NH3 decomposition was low, typically < 10% equilibrium conversion (99.7%@500°C) recorded after 1 h. All catalysts exhibited an induction period (typically ca. 10 h) with the conversion reaching a high of 67% equilibrium conversion for Cs:Fe = 0.5 and 1. The highest rate of decomposition observed was attributed to the balance between increasing the concentration of Cs without blocking the active site. Analysis of H2-TPR and XPS measurements indicated that Cs acts as an electronic promoter. Previously, Cs has been shown to act as a promoter for Ru, where Cs alters the electron density of the active site, thereby facilitating the recombination of N2 which is considered the rate determining step. In addition, XRD and N2 adsorption measurements suggest that with higher Cs loadings deactivation of the catalytic activity is due to a layer of CsOH that forms on the surface and blocks active sites. Graphic Abstract

The design and catalytic performance of molybdenum active sites on an MCM-41 framework for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

2019 ◽  
Vol 9 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Zhao-Meng Wang ◽  
Li-Juan Liu ◽  
Bo Xiang ◽  
Yue Wang ◽  
Ya-Jing Lyu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Aerobic Oxidation ◽  
Catalytic Performance ◽  
Mcm 41

The catalytic activity decreases as –(SiO)3Mo(OH)(O) > –(SiO)2Mo(O)2 > –(O)4–MoO.

Catalytic Resonance Theory: Parallel Reaction Pathway Control

2019 ◽  
Author(s):  
M. Alexander Ardagh ◽  
Manish Shetty ◽  
Anatoliy Kuznetsov ◽  
Qi Zhang ◽  
Phillip Christopher ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Active Site ◽  
Active Sites ◽  
Reaction Pathway ◽  
Control Strategies ◽  
Oscillation Amplitude ◽  
Catalytic Performance ◽  
Parallel Reaction ◽  
Resonance Theory ◽  
Static Conditions

Catalytic enhancement of chemical reactions via heterogeneous materials occurs through stabilization of transition states at designed active sites, but dramatically greater rate acceleration on that same active site is achieved when the surface intermediates oscillate in binding energy. The applied oscillation amplitude and frequency can accelerate reactions orders of magnitude above the catalytic rates of static systems, provided the active site dynamics are tuned to the natural frequencies of the surface chemistry. In this work, differences in the characteristics of parallel reactions are exploited via selective application of active site dynamics (0 < ΔU < 1.0 eV amplitude, 10<sup>-6</sup> < f < 10<sup>4</sup> Hz frequency) to control the extent of competing reactions occurring on the shared catalytic surface. Simulation of multiple parallel reaction systems with broad range of variation in chemical parameters revealed that parallel chemistries are highly tunable in selectivity between either pure product, even when specific products are not selectively produced under static conditions. Two mechanisms leading to dynamic selectivity control were identified: (i) surface thermodynamic control of one product species under strong binding conditions, or (ii) catalytic resonance of the kinetics of one reaction over the other. These dynamic parallel pathway control strategies applied to a host of chemical conditions indicate significant potential for improving the catalytic performance of many important industrial chemical reactions beyond their existing static performance.

Polymer structure and catalytic activity of ion exchangers

1981 ◽  
Vol 46 (7) ◽  
pp. 1577-1587 ◽  
Author(s):  
Karel Jeřábek
Keyword(s):  
Catalytic Activity ◽  
Ethyl Acetate ◽  
Active Sites ◽  
Crosslinking Agent ◽  
Reaction Medium ◽  
Polymer Structure ◽  
Local Concentration ◽  
Ion Exchangers ◽  
Styrene Divinylbenzene ◽  
Kinetics Of

Catalytic activity of ion exchangers prepared by partial sulphonation of styrene-divinylbenzene copolymers in reesterifications of ethyl acetate by methanol and propanol, hydrolysis of ethyl acetate and in synthesis of bisphenol A has been compared with data on polymer structure of these catalysts and with distribution of the crosslinking agent, divinylbenzene, calculated from literature data on kinetics of copolymerisation of styrene with divinylbenzene. It was found that the polymer structure of ion exchangers influences catalytic activity predominantly by changing the local concentration of acid active sites. The results obtained indicated that the effect of transport phenomena on the rate of catalytic reactions does not depend on the degree of swelling of the ion exchangers in reaction medium but it is mainly dependent on the relative affinity of reaction components to the acid groups or to the polymer skeleton.

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