Electrocatalytic Dioxygen Reduction on Underpotentially Deposited Tl on Au(111) Studied by an Active Site Blocking Strategy

Langmuir ◽  
2001 ◽  
Vol 17 (12) ◽  
pp. 3704-3711 ◽  
Author(s):  
Ilwhan Oh ◽  
Andrew A. Gewirth ◽  
Juhyoun Kwak
Keyword(s):  
Active Site ◽  
Dioxygen Reduction ◽  
Site Blocking ◽  
Underpotentially Deposited

Isozymes inhibited by active site blocking: versatility of calcium indifferent hesperidin binding to phospholipase A2 and its significance

2019 ◽  
Vol 39 (1) ◽  
pp. 60-66
Author(s):  
J. Abhithaj ◽  
K. G. Arun ◽  
C. S. Sharanya ◽  
M. Haridas ◽  
E. Jayadevi Variyar
Keyword(s):  
Phospholipase A2 ◽  
Active Site ◽  
Site Blocking

scholarly journals Enhancing the α-Cyclodextrin Specificity of Cyclodextrin Glycosyltransferase from Paenibacillus macerans by Mutagenesis Masking Subsite −7

2016 ◽  
Vol 82 (8) ◽  
pp. 2247-2255 ◽  
Author(s):  
Lei Wang ◽  
Xuguo Duan ◽  
Jing Wu
Keyword(s):  
Active Site ◽  
Wild Type ◽  
Cyclodextrin Glycosyltransferase ◽  
Wild Type Enzyme ◽  
Widespread Application ◽  
Content Type ◽  
Hydrogen Bonding Interactions ◽  
Paenibacillus Macerans ◽  
Site Blocking ◽  
Cyclodextrin Production

ABSTRACTCyclodextrin glycosyltransferases (CGTases) (EC 2.4.1.19) catalyze the conversion of starch or starch derivates into mixtures of α-, β-, and γ-cyclodextrins. Because time-consuming and expensive purification procedures hinder the widespread application of single-ingredient cyclodextrins, enzymes with enhanced specificity are needed. In this study, we tested the hypothesis that the α-cyclodextrin selectivity ofPaenibacillus maceransα-CGTase could be augmented by masking subsite −7 of the active site, blocking the formation of larger cyclodextrins, particularly β-cyclodextrin. Five single mutants and three double mutants designed to remove hydrogen-bonding interactions between the enzyme and substrate at subsite −7 were constructed and characterized in detail. Although the rates of α-cyclodextrin formation varied only modestly, the rate of β-cyclodextrin formation decreased dramatically in these mutants. The increase in α-cyclodextrin selectivity was directly proportional to the increase in the ratio of theirkcatvalues for α- and β-cyclodextrin formation. The R146A/D147P and R146P/D147A double mutants exhibited ratios of α-cyclodextrin to total cyclodextrin production of 75.1% and 76.1%, approximately one-fifth greater than that of the wild-type enzyme (63.2%), without loss of thermostability. Thus, these double mutants may be more suitable for the industrial production of α-cyclodextrin than the wild-type enzyme. The production of β-cyclodextrin by these mutants was almost identical to their production of γ-cyclodextrin, which was unaffected by the mutations in subsite −7, suggesting that subsite −7 was effectively blocked by these mutations. Further increases in α-cyclodextrin selectivity will require identification of the mechanism or mechanisms by which these small quantities of larger cyclodextrins are formed.

scholarly journals Inhibition of Plasma Kallikrein by a Highly Specific Active Site Blocking Antibody

2014 ◽  
Vol 289 (34) ◽  
pp. 23596-23608 ◽  
Author(s):  
Jon A. Kenniston ◽  
Ryan R. Faucette ◽  
Diana Martik ◽  
Stephen R. Comeau ◽  
Allison P. Lindberg ◽  
...  
Keyword(s):  
Active Site ◽  
Plasma Kallikrein ◽  
Blocking Antibody ◽  
Site Blocking

Structural and mechanistic basis for the high activity of Fe–N–C catalysts toward oxygen reduction

2016 ◽  
Vol 9 (7) ◽  
pp. 2418-2432 ◽  
Author(s):  
Jingkun Li ◽  
Shraboni Ghoshal ◽  
Wentao Liang ◽  
Moulay-Tahar Sougrati ◽  
Frédéric Jaouen ◽  
...  
Keyword(s):  
Redox Potential ◽  
Oxygen Reduction ◽  
High Activity ◽  
Active Site ◽  
Blocking Effect ◽  
Dynamic Nature ◽  
Mechanistic Basis ◽  
Site Blocking

The biomimetic dynamic nature of the Fe–N–C active site with a near-optimal Fe2+/3+redox potential facilitates ORR by balancing the site-blocking effect and O2dissociation.

scholarly journals Allosteric control of Ubp6 and the proteasome via a bidirectional switch

2021 ◽  
Author(s):  
Ka Ying Sharon Hung ◽  
Sven Klumpe ◽  
Markus R. Eisele ◽  
Suzanne Elsasser ◽  
Geng Tian ◽  
...  
Keyword(s):  
Active Site ◽  
Proteasome Inhibition ◽  
Conformational State ◽  
Deubiquitinating Enzyme ◽  
Deubiquitinating Enzymes ◽  
New Paradigm ◽  
Allosteric Control ◽  
Topological Features ◽  
Simultaneous Control ◽  
Site Blocking

The proteasome is the principal cellular protease, and recognizes target proteins that have been covalently marked by ubiquitin chains. The ubiquitin signal is subject to rapid editing at the proteasome, allowing it to reject substrates based on topological features of their attached ubiquitin chains. Editing is mediated by a key regulator of the proteasome, deubiquitinating enzyme Ubp6. The proteasome activates Ubp6, whereas Ubp6 inhibits the proteasome–both by deubiquitinating proteasome-bound ubiquitin conjugates, and through a noncatalytic effect that does not involve deubiquitination. We report mutants in both Ubp6 and proteasome subunit Rpt1 that abrogate Ubp6 activation. The Ubp6 mutations fall within its ILR element, defined here, which is conserved from yeast to mammals. The ILR is a component of the BL1 blocking loop, other parts of which obstruct ubiquitin access to the catalytic groove in free Ubp6. Rpt1 docking at the ILR opens the catalytic groove by rearranging not only BL1 but also a novel network of three directly interconnected active-site-blocking loops. Ubp6 activation and noncatalytic proteasome inhibition by Ubp6 are linked in that they were eliminated by the same Ubp6 and Rpt1 mutations. Ubp6 and ubiquitin together drive the proteasome into a unique conformational state associated with proteasome inhibition. Our results identify a multicomponent allosteric switch that exerts simultaneous control over the activity of both Ubp6 and the proteasome, and suggest that their active states are in general mutually exclusive. The findings lead to a new paradigm for allosteric control of deubiquitinating enzymes.

Suppressing the active site-blocking impact of ligands of Ni6(SR)12 clusters with the assistance of NH3 on catalytic hydrogenation of nitriles

Nanoscale ◽  
2018 ◽  
Vol 10 (41) ◽  
pp. 19375-19382 ◽  
Author(s):  
Xiaoqi Chai ◽  
Tao Li ◽  
Mingyang Chen ◽  
Rongchao Jin ◽  
Weiping Ding ◽  
...  
Keyword(s):  
Catalytic Hydrogenation ◽  
Active Site ◽  
Shielding Effect ◽  
Site Blocking ◽  
Hydrogenation Of Nitriles

The activity of Ni6(SR)12 for nitriles hydrogenation is enhanced with the assistance of NH3 that suppresses the ligand shielding effect.

scholarly journals NOx and propene conversion on La0.85Sr0.15MnO3+d/Ce0.9Gd0.1O1.95 symmetrical cells

2017 ◽  
Author(s):  
Anja Z. Friedberg ◽  
Kent Kammer Hansen
Keyword(s):  
Catalytic Activity ◽  
Active Site ◽  
Catalytic Reduction ◽  
Electrochemical Promotion ◽  
Reduction Of No ◽  
No Conversion ◽  
Propene Conversion ◽  
Catalytically Active ◽  
Reduction Of Nox ◽  
Site Blocking

<p class="PaperAbstract"><span lang="EN-US">The catalytic electrochemical reduction of NO with propene was investigated on La<sub>0.85</sub>Sr<sub>0.15</sub>MnO<sub>3+d</sub>/Ce<sub>0.9</sub>Gd<sub>0.1</sub>O<sub>1.95</sub> symmetrical cells. The electrodes were infiltrated with BaO and Pt. The cells were catalytically active towards the selective catalytic reduction of NO<sub>x</sub> with propene, but BaO infiltration lowered the NO conversion, probably because of active-site blocking on La<sub>0.85</sub>Sr<sub>0.15</sub>MnO<sub>3+d</sub>. Pt infiltration enhanced the reduction of NOx with propene. When a voltage was applied to the cell with BaO infiltrated electrodes, the NO conversion increased in absence and presence of propene in the feed gas and presence of 10</span><span lang="EN-US">% O<sub>2</sub>. The addition of propene into the feed gas did not enhance the conversion of NO when the electrodes were infiltrated with BaO. When platinum was co-infiltrated with BaO, the catalytic activity towards the reduction of NO with propene was enhanced. However, almost no effect was observed when a voltage was applied. Additionally, when the cells were infiltrated with Pt, an electrochemical promotion was observed with respect to CO<sub>2</sub> formation.</span></p>

Characterisation of Epitopes on Human Tissue Plasminogen Activator Recognised by a Group of Monoclonal Antibodies

1985 ◽  
Vol 53 (01) ◽  
pp. 045-050 ◽  
Author(s):  
Ian R MacGregor ◽  
Lisel R Micklem ◽  
Keith James ◽  
Duncan S Pepper
Keyword(s):  
Monoclonal Antibodies ◽  
Plasminogen Activator ◽  
Tissue Plasminogen Activator ◽  
Active Site ◽  
Amidolytic Activity ◽  
Binding Properties ◽  
Tissue Plasminogen ◽  
Site Blocking ◽  
Melanoma Tissue ◽  
Active Site Histidine

SummarySeven mouse monoclonal antibodies have been produced against human melanoma tissue plasminogen activator (t-PA). They were specifically bound to 125I t-PA but not 125I urokinase (u-PA) and inhibited t-PA, but not u-PA, activity in plasminogen- rich 125I fibrin wells. Three of the antibodies directly inhibited the amidolytic activity of t-PA and the two most effective also bound near the active site histidine residue as determined by competition experiments using active site blocking agents. Several antibodies interfered with the fibrin binding properties of t-PA. One antibody neither interacted with the active site nor inhibited fibrin binding but still effectively quenched t-PA activity in fibrin wells suggesting that it masks another region of the molecule necessary for effective biological activity.

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