scholarly journals The catalytic activity of monomeric yeast hexokinase A

1977 ◽  
Vol 161 (1) ◽  
pp. 181-183
Author(s):  
B P Yip ◽  
F B Rudolph
Keyword(s):  
Catalytic Activity ◽  
Monomeric Form ◽  
Catalytically Active ◽  
Yeast Hexokinase

It has been suggested [Williams, D.C. & Jones, J.G. (1976) Biochem. J. 155, 661-667] that monomeric hexokinase isoenzyme A is not catalytically active. We here present data from reacting-enzyme sedimentation, dissociation experiments and from previous studies which are consistent with the monomeric form possessing catalytic activity.

scholarly journals Dissociation and catalysis in yeast hexokinase A.

1976 ◽  
Vol 155 (3) ◽  
pp. 661-667 ◽  
Author(s):  
D C Williams ◽  
J G Jones
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Ternary Complex ◽  
Specific Activity ◽  
Temperature Dependent ◽  
Gradual Decline ◽  
Experimental Conditions ◽  
Progress Curve ◽  
Catalytically Active ◽  
Yeast Hexokinase

1. The specific activity of yeast hexokinase A depends on the concentration of the protein in the solution being assayed. When a solution containing 13.5 mg of hexokinase A/ml is diluted 10-100-fold at various values of pH and temperature, there is a gradual decline in the specific activity of the enzyme until an equilibrium value is reached, which varies with the chosen experimental conditions. 2. The catalytic activity lost when hexokinase A (1 mg/ml) is incubated at 30degreesC is recovered by lowering the temperature to 25degreesC. 3. These concentration- and temperature-dependent phenomena are consistent with the existence of a monomer-dimer equilibrium in which the dimer alone is the catalytic form of the enzyme. 4. Glucose alone prevents the decline in specific activity of hexokinase A after dilution, but it does not re-activate dilute solutions solutions of the enzyme. It is concluded that glucose binds to both the dimer and the monomer and prevents both association and dissociation. 5. The progress curve describing the phosphorylation of glucose catalysed by hexokinase A does not attain a steady state. It is possible that dissociation of catalytically active dimers in a ternary complex with glucose and ATP (or glucose 6-phosphate and ADP) could explain the non-linearity of this progress curve.

Hydrogen peroxide decomposition on a two-component CuO-Cr2O3 catalyst

1988 ◽  
Vol 53 (8) ◽  
pp. 1636-1646 ◽  
Author(s):  
Viliam Múčka ◽  
Kamil Lang
Keyword(s):  
Hydrogen Peroxide ◽  
Catalytic Activity ◽  
Extreme Values ◽  
Catalytic Properties ◽  
Active Components ◽  
Catalytic Systems ◽  
Heterogeneous Catalytic ◽  
Peroxide Decomposition ◽  
Two Component ◽  
Catalytically Active

Some physical and catalytic properties of the two-component copper(II)oxide-chromium(III)oxide catalyst with different content of both components were studied using the decomposition of the aqueous solution of hydrogen peroxide as a testing reaction. It has been found that along to both basic components, the system under study contains also the spinel structure CuCr2O4, chromate washable by water and hexavalent ions of chromium unwashable by water. The soluble chromate is catalytically active. During the first period of the reaction the equilibrium is being established in both homogeneous and heterogeneous catalytic systems. The catalytic activity as well as the specific surface area of the washed solid is a non-monotonous function of its composition. It seems highly probable that the extreme values of both these quantities are not connected with the detected admixtures in the catalytic system. The system under study is very insensitive with regard to the applied doses of gamma radiation. Its catalytic properties are changed rather significantly after the thermal treatment and particularly after the partial reduction to low degree by hydrogen. The observed changes of the catalytic activity of the system under study are very probably in connection with the changes of the valence state of the catalytically active components of the catalyst.

scholarly journals Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

2021 ◽  
Author(s):  
Petar Djinović ◽  
Janez Zavašnik ◽  
Janvit Teržan ◽  
Ivan Jerman
Keyword(s):  
Catalytic Activity ◽  
Activated Carbon ◽  
Oxidative Dehydrogenation ◽  
Active Phase ◽  
Lattice Oxygen ◽  
Chemisorbed Oxygen ◽  
Catalytically Active ◽  
Temperature Programmed ◽  
Propane Cracking

AbstractCeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested in propane oxidative dehydrogenation using CO2. Complete oxidation of propane to CO and CO2 is favoured by lattice oxygen of CeO2. The temperature programmed experiments show the ~ 4 nm AC supported CeO2 crystallites become more susceptible to reduction by propane, but less prone to re-oxidation with CO2 compared to bulk CeO2. Catalytic activity of CeVO4/AC catalysts requires a 1–2 nm amorphous CeVO4 layer. During reaction, the amorphous CeVO4 layer crystallises and several atomic layers of carbon cover the CeVO4 surface, resulting in deactivation. During reaction, V2O5 is irreversibly reduced to V2O3. The lattice oxygen in bulk V2O5 favours catalytic activity and propene selectivity. Bulk V2O3 promotes only propane cracking with no propene selectivity. In VOx/AC materials, vanadium carbide is the catalytically active phase. Propane dehydrogenation over VC proceeds via chemisorbed oxygen species originating from the dissociated CO2. Graphic Abstract

From Ru nanoparticle-encapsulated metal–organic frameworks to highly catalytically active Cu/Ru nanoparticle-embedded porous carbon

2017 ◽  
Vol 5 (10) ◽  
pp. 4835-4841 ◽  
Author(s):  
Pradip Pachfule ◽  
Xinchun Yang ◽  
Qi-Long Zhu ◽  
Nobuko Tsumori ◽  
Takeyuki Uchida ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Temperature ◽  
Porous Carbon ◽  
Metal Organic Frameworks ◽  
Ammonia Borane ◽  
Carbon Composites ◽  
High Catalytic Activity ◽  
Catalytically Active ◽  
Metal Organic

High-temperature pyrolysis of Ru nanoparticle-encapsulated MOF (Ru@HKUST-1) afforded ultrafine Cu/Ru nanoparticle-embedded porous carbon composites (Cu/Ru@C), which show high catalytic activity for ammonia borane hydrolysis.

Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions

2011 ◽  
Vol 89 (8) ◽  
pp. 939-947 ◽  
Author(s):  
Irena Mihailova ◽  
Dimitar Mehandjiev
Keyword(s):  
Catalytic Activity ◽  
Solid Phase ◽  
Sol Gel ◽  
Cobalt Content ◽  
Octahedral Coordination ◽  
Tetrahedral Coordination ◽  
Oxidation Reactions ◽  
Oxidation Of Co ◽  
Phase Synthesis ◽  
Catalytically Active

Two calcium–cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca2CoSi2O7), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol–gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.

Enhanced catalytic activity of cobalt catalysts for Fischer–Tropsch synthesis via carburization and hydrogenation and its application to regeneration

2016 ◽  
Vol 6 (12) ◽  
pp. 4594-4600 ◽  
Author(s):  
Geunjae Kwak ◽  
Du-Eil Kim ◽  
Yong Tae Kim ◽  
Hae-Gu Park ◽  
Seok Chang Kang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Material ◽  
Catalytic Performance ◽  
Tropsch Synthesis ◽  
Cobalt Catalysts ◽  
Fischer Tropsch ◽  
Fischer Tropsch Synthesis ◽  
Cobalt Carbide ◽  
Catalytically Active

In Fischer–Tropsch synthesis (FTS), cobalt carbide (Co2C) is not a catalytically active material, but rather an undesired cobalt phase associated with low catalytic performance.

Nitrogen and phosphorus modification to enhance the catalytic activity of biomass-derived carbon toward the oxygen reduction reaction

2020 ◽  
Vol 4 (6) ◽  
pp. 2707-2717 ◽  
Author(s):  
Lei Han ◽  
Xingyu Cui ◽  
Yanyan Liu ◽  
Guosheng Han ◽  
Xianli Wu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Synergistic Effect ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Carbon ◽  
Reduction Reaction ◽  
Nitrogen And Phosphorus ◽  
Catalytically Active ◽  
Air Battery ◽  
Phosphorus Modification

N, P heteroatoms are doped into the carbon derived from Fructus azedarach precursor. The successful application in zinc–air battery illustrates that the N, P synergistic effect makes a bright future for the development of catalytically active carbon.

scholarly journals In Vivo Dimerization of Types 1, 2, and 3 Iodothyronine Selenodeiodinases

Endocrinology ◽  
2003 ◽  
Vol 144 (3) ◽  
pp. 937-946 ◽  
Author(s):  
Cyntia Curcio-Morelli ◽  
Balazs Gereben ◽  
Ann Marie Zavacki ◽  
Brian W. Kim ◽  
Stephen Huang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Western Blot ◽  
Relative Molecular Mass ◽  
Disulfide Bridges ◽  
Wild Type ◽  
Human Embryonic Kidney ◽  
Cell Lysate ◽  
Sds Page ◽  
Catalytically Active

The goal of the present investigation was to test the hypothesis that types 1, 2, and 3 iodothyronine selenodeiodinases (D1, D2, and D3) can form homodimers. The strategy included transient coexpression of wild-type (wt) deiodinases (target), and FLAG-tagged alanine or cysteine mutants (bait) in human embryonic kidney epithelial cells. SDS-PAGE of the immunoprecipitation pellet of 75Se-labeled cell lysates using anti-FLAG antibody revealed bands of the correct sizes for the respective wt enzymes, which corresponded to approximately 2–5% of the total deiodinase protein in the cell lysate. Western blot analysis with anti-FLAG antibody of lysates of cells transiently expressing individual FLAG-tagged-cysteine deiodinases revealed specific monomeric bands for each deiodinase and additional minor bands of relative molecular mass (Mr) of 55,000 for D1, Mr 62,000 for D2, and Mr 65,000 for D3, which were eliminated by 100 mm dithiothreitol at 100 C. Anti-FLAG antibody immunodepleted 10% of D1 and 38% of D2 activity from lysates of cells coexpressing inactive FLAG-tagged Ala mutants and the respective wt enzymes (D1 or D2) but failed to immunodeplete wtD3 activity. D1 or D2 activities were present in these respective pellets. We conclude 1) that overexpressed selenodeiodinases can homodimerize probably through disulfide bridges; and 2) at least for D1 and D2, monomeric forms are catalytically active, demonstrating that only one wt monomer partner is required for catalytic activity of these two deiodinases.

Catalytically active designer crown-jewel Pd-based nanostructures encapsulated in metal–organic frameworks

2017 ◽  
Vol 53 (6) ◽  
pp. 1184-1187 ◽  
Author(s):  
Liyu Chen ◽  
Weihao Huang ◽  
Xiujun Wang ◽  
Zhijie Chen ◽  
Xianfeng Yang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Metal Organic Frameworks ◽  
Catalytically Active ◽  
Metal Organic

A series of Pd based bimetallic NPs with unique “crown-jewel” structure and tunable composition have been successfully fabricated inside the MOF pores, exhibiting superior catalytic activity and stability.

Three-Dimensional Periodic Hematite Photocatalysts Fabricating by Direct Writing Method

2014 ◽  
Vol 1025-1026 ◽  
pp. 621-627
Author(s):  
Qin Mei Peng ◽  
Bo Li ◽  
Jin Wang ◽  
Ji Jiao Li ◽  
Ji Zhou
Keyword(s):  
Methylene Blue ◽  
Catalytic Activity ◽  
Organic Contaminants ◽  
Degradation Rate ◽  
Sol Gel ◽  
Three Dimensional ◽  
High Catalytic Activity ◽  
Direct Writing ◽  
Catalytically Active ◽  
Gel Technique

Three-dimensional (3-D) periodic hematite scaffold was successfully fabricated by direct writing method as a catalyst for degradation of organic contaminants. Photo-catalytically active α-Fe2O3 nanoparticles have been synthesized by sol-gel technique. Aqueous slurries of iron oxides were freeform fabricated to produce hematite scaffolds with a 3-D periodic architecture and multiscale porosity. The catalytic activity of the hematite scaffolds was evaluated in the degradation of Methylene Blue (MB). It was found that the degradation rate of MB dye was over 83%. The result strongly indicates that the hematite scaffolds exhibits a high catalytic activity. Moreover, this work provides an important step forward in the creation of suitable structures for photocatalyst.

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