High Catalytic Activities of RENi5–xAlx (RE = La, Er) and Low Activity of Mg2Ni Following Hydrogen Uptake: The Role of Absorbed Hydrogen

2021 ◽  
Author(s):  
Ryota Tsukuda ◽  
Takayuki Kojima ◽  
Ya Xu ◽  
Chikashi Nishimura ◽  
Marian Krajčí ◽  
...  
Keyword(s):  
Hydrogen Uptake ◽  
Catalytic Activities ◽  
Low Activity

scholarly journals Functional cross-talk between allosteric effects of activating and inhibiting ligands underlies PKM2 regulation

2018 ◽  
Author(s):  
Jamie A. Macpherson ◽  
Alina Theisen ◽  
Laura Masino ◽  
Louise Fets ◽  
Paul C. Driscoll ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
High Activity ◽  
Pyruvate Kinase ◽  
Cross Talk ◽  
Glycolytic Enzyme ◽  
Computational Framework ◽  
Allosteric Inhibitor ◽  
Fructose 1,6 Bisphosphate ◽  
Low Activity

ABSTRACTAllosteric regulation is central to the role of the glycolytic enzyme pyruvate kinase M2 (PKM2) in cellular metabolism. Multiple activating and inhibitory allosteric ligands regulate PKM2 activity by controlling the equilibrium between high activity tetramers and low activity dimers and monomers. However, it remains elusive how allosteric inputs upon simultaneous binding of different ligands are integrated to regulate PKM2 activity. Here, we show that, in the presence of the allosteric inhibitor L-phenylalanine (Phe), the activator fructose 1,6-bisphosphate (FBP) can induce PKM2 tetramerisation, but fails to maximally increase enzymatic activity. Guided by a new computational framework we developed to identify residues that mediate FBP-induced allostery, we generated two PKM2 mutants, A327S and C358A, in which activation by FBP remains intact but cannot be attenuated by Phe. Our findings demonstrate a role for residues involved in FBP-induced allostery in enabling the integration of allosteric input from Phe and reveal a mechanism that underlies the co-ordinate regulation of PKM2 activity by multiple allosteric ligands.

scholarly journals Activities and some properties of 5′-nucleotidase, adenosine kinase and adenosine deaminase in tissues from vertebrates and invertebrates in relation to the control of the concentration and the physiological role of adenosine

1978 ◽  
Vol 174 (3) ◽  
pp. 965-977 ◽  
Author(s):  
J R S Arch ◽  
E A Newsholme
Keyword(s):  
Adenosine Deaminase ◽  
Physiological Role ◽  
Adenosine Kinase ◽  
British Library ◽  
Adenosine Concentration ◽  
Effects Of Ph ◽  
The Difference ◽  
Low Activity

1. The maximal activities of 5′-nucleotidase, adenosine kinase and adenosine deaminase together with the Km values for their respective substrates were measured in muscle, nervous tissue and liver from a large range of animals to provide information on the mechanism of control of adenosine concentration in the tissues. 2. Detailed evidence that the methods used were optimal for the extraction and assay of these enzymes has been deposited as Supplementary Publication SUP 50088 (16pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K.,from whom copies can be obtained on the terms indicated in Biochem. J. (1978), 169, 5. This evidence includes the effects of pH and temperature on the activities of the enzymes. 3. In many tissues, the activities of 5′-nucleotidase were considerably higher than the sum of the activities of adenosine kinase and deaminase, which suggests that the activity of the nucleotidase must be markedly inhibited in vivo so that adenosine does not accumulate. In the tissues in which comparison is possible, the Km of the nucleotidase is higher than the AMP content of the tissue, and since some of the latter may be bound within the cell, the low concentration of substrate may, in part, be responsible for a low activity in vivo. 4. In most tissues and animals investigated, the values of the Km of adenosine kinase for adenosine are between one and two orders of magnitude lower than those for the deaminase. It is suggested that 5′-nucleotidase and adenosine kinase are simultaneously active so that a substrate cycle between AMP and adenosine is produced: the difference in Km values between kinase and deaminase indicates that, via the cycle, small changes in activity of kinase or nucleotidase produce large changes in adenosine concentration. 5. The activities of adenosine kinase or deaminase from vertebrate muscles are inversely correlated with the activities of phosphorylase in these muscles. Since the magnitude of the latter activities are indicative of the anaerobic nature of muscles, this negative correlation supports the hypothesis that an important role of adenosine is the regulation of blood flow in the aerobic muscles.

scholarly journals Role of Microstructure in Susceptibility to Hydrogen Embrittlement of X70 Microalloyed Steel

2014 ◽  
Vol 783-786 ◽  
pp. 961-966
Author(s):  
Daniel Hejazi ◽  
Ahmed A. Saleh ◽  
Ayesha Haq ◽  
Druce Dunne ◽  
Andrzej Calka ◽  
...  
Keyword(s):  
Microalloyed Steel ◽  
Hydrogen Uptake ◽  
Internal Damage ◽  
Steel Microstructure ◽  
Back Scattering ◽  
Hydrogen Induced Cracking ◽  
Steel Processing ◽  
Bainite Microstructure ◽  
Prior Processing

The effect of phases and steel processing on hydrogen uptake (diffusible and residual), surface and internal damage were evaluated using optical and scanning electron microscopy. The results have shown the fastest formation of blisters in ferrite-pearlite microstructure of strip, followed by equaixed ferrite-pearlite microstructure in normalised condition, then by ferrite-bainite microstructure. No blistering was observed in heat affected zone samples for up to 24 hrs charging. Analysis of hydrogen-induced cracking using electron back scattering diffraction has revealed that crack propagation has predominantly intragranular character without a clear preference on {001}, {110}, {112} and {123} planes and is independent of the steel microstructure and prior processing.

Role of lattice defects in catalytic activities of graphene clusters for fuel cells

2015 ◽  
Vol 17 (26) ◽  
pp. 16733-16743 ◽  
Author(s):  
Lipeng Zhang ◽  
Quan Xu ◽  
Jianbing Niu ◽  
Zhenhai Xia
Keyword(s):  
Fuel Cells ◽  
Electronic Structures ◽  
Chemical Properties ◽  
Lattice Defects ◽  
Physical And Chemical Properties ◽  
Catalytic Activities ◽  
Physical And Chemical ◽  
And Chemical Properties

Defects are common but important in graphene, which could significantly tailor the electronic structures and physical and chemical properties.

Role of Intermetallic Precipitates in Hydrogen Uptake of Zircaloy-2

1996 ◽  
Vol 33 (12) ◽  
pp. 944-949 ◽  
Author(s):  
Yuji HATANO ◽  
Kanetsugu ISOBE ◽  
Ryuji HITAKA ◽  
Masayasu SUGISAKI
Keyword(s):  
Hydrogen Uptake ◽  
Intermetallic Precipitates

scholarly journals SULFATION PATHWAYS: Formation and hydrolysis of sulfonated estrogens in the porcine testis and epididymis

2018 ◽  
Vol 61 (2) ◽  
pp. M13-M25 ◽  
Author(s):  
G Schuler ◽  
Y Dezhkam ◽  
L Tenbusch ◽  
MC Klymiuk ◽  
B Zimmer ◽  
...  
Keyword(s):  
Leydig Cells ◽  
De Novo ◽  
Rete Testis ◽  
New Information ◽  
Testicular Steroidogenesis ◽  
High Concentrations ◽  
Hydrolysis Of ◽  
Low Activity ◽  
Porcine Testis

Boars exhibit high concentrations of sulfonated estrogens (SE) mainly originating from the testicular-epididymal compartment. Intriguingly, in porcine Leydig cells, sulfonation of estrogens is colocalized with aromatase and steroid sulfatase (STS), indicating that de novo synthesis of unconjugated estrogens (UE), their sulfonation and hydrolysis of SE occur within the same cell type. So far in boars no plausible concept concerning the role of SE has been put forward. To obtain new information on SE formation and hydrolysis, the porcine testicular-epididymal compartment was screened for the expression of the estrogen-specific sulfotransferase SULT1E1 and STS applying real-time RT-qPCR, Western blot and immunohistochemistry. The epididymal head was identified as the major site of SULT1E1 expression, whereas in the testis, it was virtually undetectable. However, SE tissue concentrations are clearly consistent with the testis as the predominant site of estrogen sulfonation. Results from measurements of estrogen sulfotransferase activity indicate that in the epididymis, SULT1E1 is the relevant enzyme, whereas in the testis, estrogens are sulfonated by a different sulfotransferase with a considerably lower affinity. STS expression and activity was high in the testis (Leydig cells, rete testis epithelium) but also present throughout the epididymis. In the epididymis, SULT1E1 and STS were colocalized in the ductal epithelium, and there was evidence for their apocrine secretion into the ductal lumen. The results suggest that in porcine Leydig cells, SE may be produced as a reservoir to support the levels of bioactive UE via the sulfatase pathway during periods of low activity of the pulsatile testicular steroidogenesis.

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