scholarly journals Cover Feature: Thermal Adaptation of Enzymes: Impacts of Conformational Shifts on Catalytic Activation Energy and Optimum Temperature (Chem. Eur. J. 44/2020)

2020 ◽  
Vol 26 (44) ◽  
pp. 9657-9657
Author(s):  
Irene Maffucci ◽  
Damien Laage ◽  
Fabio Sterpone ◽  
Guillaume Stirnemann
Keyword(s):  
Activation Energy ◽  
Thermal Adaptation ◽  
Optimum Temperature ◽  
Catalytic Activation ◽  
Conformational Shifts

scholarly journals Synthesis and Characterisation of Structural and Electrical Properties of CuMn2O4 Spinel Compound

2021 ◽  
pp. 1-4
Author(s):  
Rasha Yousef ◽  
Alaa Nassif ◽  
Abla Al-Zoubi ◽  
Nasser Al-Din
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Electrical Properties ◽  
Optimum Temperature ◽  
Prepared Compound ◽  
Solid State Method ◽  
Structural And Electrical Properties ◽  
Cubic Structure ◽  
Experimental Density ◽  
Scherrer Method

CuMn2O4 was synthesized by the solid-state method. MnO2 and CuO were used as precursors. The optimum temperature of synthesis was 850°C. XRD results showed that the prepared compound had a cubic structure with Fd3 ̅m space group. The lattice constant and unit cell volume were a=8.359Å and V=584.14A°3 respectively. The grain size was calculated by the Debye-Scherrer method and was 33.49 nm for CuMn2O4 annealed at 850°C. The experimental density was calculated and compared to the theoretical density. The results were ρt= 5.399 gr/cm3 and ρE = 5.24 gr/cm3. The electrical properties of the compound showed that it behaves like a semiconductor, and the activation energy of the compound was 0.1535 eV. KEYWORDS Activation energy, copper manganite (CuMO), mixed oxide, solid-state reaction, spinel

scholarly journals Purification and general properties of δ-aminolaevulate dehydratase from Nicotiana tabacum L.

1969 ◽  
Vol 114 (2) ◽  
pp. 331-337 ◽  
Author(s):  
A. S. Shetty ◽  
G. W. Miller
Keyword(s):  
Activation Energy ◽  
Nicotiana Tabacum ◽  
Phosphate Buffer ◽  
Potassium Phosphate ◽  
Optimum Temperature ◽  
Thiol Groups ◽  
Potassium Phosphate Buffer ◽  
Tobacco Leaves ◽  
General Properties ◽  
Nicotiana Tabacum L

1. δ-Aminolaevulate dehydratase (EC 4.2.1.24) was purified 80-fold from tobacco leaves and its properties were studied. 2. The enzyme had optimum pH7·4 in potassium phosphate buffer, Km6·25×10−4m at 37° and pH7·4, optimum temperature 45° and an activation energy of 11100 cal./mole. 3. The enzyme lost activity when prepared in the absence of cysteine, and this activity was only partly restored by the later addition of thiols. Reagents for thiol groups inactivated the enzyme. 4. Mg2+ was essential for activity, and EDTA and Fe2+ were inhibitory; Mn2+ was an activator or an inhibitor depending on the concentration.

β-Galactosidase from Bacillus stearothermophilus

1976 ◽  
Vol 22 (6) ◽  
pp. 817-825 ◽  
Author(s):  
Richard E. Goodman ◽  
Dennis M. Pederson
Keyword(s):  
Activation Energy ◽  
Molecular Weight ◽  
Gel Electrophoresis ◽  
Bacillus Stearothermophilus ◽  
Thermal Inactivation ◽  
Ph Dependence ◽  
Temperature Sensitive ◽  
Optimum Temperature ◽  
Arrhenius Activation Energy ◽  
Ph Optimum

Several strains of thermophilic aerobic spore-forming bacilli synthesize β-galactosidase (EC 3.2.1.23) constitutively. The constitutivity is apparently not the result of a temperature-sensitive repressor. The β-galactosidase from one strain, investigated in cell-free extracts, has a pH optimum between 6.0 and 6.4 and a very sharp pH dependence on the acid side of its optimum. The optimum temperature for this enzyme is 65 °C and the Arrhenius activation energy is about 24 kcal/mol below 47 °C and 16 kcal/mol above that temperature. At 55 °C the Km is 0.11 M for lactose and 9.8 × 10−3 M for o-nitrophenyl-β-D-galactopyranoside. The enzyme is strongly product-inhibited by galactose (Ki = 2.5 × 10−3 M). It is relatively stable at 50 °C, losing only half of its activity after 20 days at this temperature. At 60 °C more than 60% of the activity is lost in 10 min. However, the enzyme is protected somewhat against thermal inactivation by protein, and in the presence of 4 mg/ml of bovine serum albumin the enzyme is only 18% inactivated in 10 min at 60 °C. Its molecular weight, estimated by disc gel electrophoresis, is 215 000.

Thermal adaptation and acclimation of ecotypic populations of Spirodela polyrhiza (Lemnaceae): thermostability and apparent activation energy of NAD malate dehydrogenase

1981 ◽  
Vol 59 (6) ◽  
pp. 1061-1068 ◽  
Author(s):  
Dominique Davidson ◽  
Jean-Pierre Simon
Keyword(s):  
Activation Energy ◽  
Malate Dehydrogenase ◽  
Aquatic Plant ◽  
Thermal Adaptation ◽  
Terrestrial Plants ◽  
Spirodela Polyrhiza ◽  
Average Temperature ◽  
Origin Activation ◽  
Regulatory Systems ◽  
Bodies Of Water

Eleven ecotypes of Spirodela polyrhiza (L.) Schleid., an aquatic plant possessing an extensive geographic distribution, were studied to detect adaptive and acclimatory metabolic changes through a study of the thermostability and activation energy of malate dehydrogenase. Colonies were grown under controlled conditions with temperature (18, 23, and 28 °C) as the only variable. Thermostability is found to be affected by experimental temperatures (acclimation) but not by origin temperatures; there is genetic differentiation but related to some other environmental conditions than average temperature at the site of origin. Activation energy is unaffected by experimental temperatures or origin. It is suggested that, as S. polyrhiza naturally grows in bodies of water, it is less exposed to temperature variations than terrestrial plants, but is more affected by other physicochemical environmental factors; its main metabolic regulatory systems do not appear to be associated with thermal controls.

scholarly journals Variation in Responses of Photosynthesis and Apparent Rubisco Kinetics to Temperature in Three Soybean Cultivars

Plants ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 443
Author(s):  
Bunce
Keyword(s):  
Activation Energy ◽  
Co2 Concentration ◽  
C3 Plants ◽  
Optimum Temperature ◽  
Response Curves ◽  
Soybean Cultivars ◽  
In Vivo Assays ◽  
Glycine Max L ◽  
Temperature Responses

Recent in vivo assays of the responses of Rubisco to temperature in C3 plants have revealed substantial diversity. Three cultivars of soybean (Glycine max L. Merr.), Holt, Fiskeby V, and Spencer, were grown in indoor chambers at 15, 20, and 25 °C. Leaf photosynthesis was measured over the range of 15 to 30 °C, deliberately avoiding higher temperatures which may cause deactivation of Rubisco, in order to test for differences in temperature responses of photosynthesis, and to investigate in vivo Rubisco kinetic characteristics responsible for any differences observed. The three cultivars differed in the optimum temperature for photosynthesis (from 15 to 30 °C) at 400 mmol mol−1 external CO2 concentration when grown at 15 °C, and in the shapes of the response curves when grown at 25 °C. The apparent activation energy of the maximum carboxylation rate of Rubisco differed substantially between cultivars at all growth temperatures, as well as changing with growth temperature in two of the cultivars. The activation energy ranged from 58 to 84 kJ mol−1, compared with the value of 64 kJ mol−1 used in many photosynthesis models. Much less variation in temperature responses occurred in photosynthesis measured at nearly saturating CO2 levels, suggesting more diversity in Rubisco than in electron transport thermal properties among these soybean cultivars.

scholarly journals Variation in Responses of Photosynthesis and Apparent Rubisco Kinetics to Temperature in Three Soybean Cultivars

2019 ◽  
Author(s):  
James Bunce
Keyword(s):  
Activation Energy ◽  
Co2 Concentration ◽  
C3 Plants ◽  
Optimum Temperature ◽  
Response Curves ◽  
Soybean Cultivars ◽  
In Vivo Assays ◽  
Glycine Max L ◽  
Temperature Responses

Recent in vivo assays of the responses of Rubisco to temperature in C3 plants have revealed substantial diversity. Three cultivars of soybean (Glycine max L. Merr.), Holt, Fiskeby V, and Spencer, were grown in indoor chambers at 15, 20, and 25 oC. Leaf photosynthesis was measured over the range of 15 to 30 oC, deliberately avoiding higher temperatures which may cause deactivation of Rubisco, in order to test for differences in temperature responses of photosynthesis, and to investigate in vivo Rubisco kinetic characteristics responsible for any differences observed. The three cultivars differed in the optimum temperature for photosynthesis (from 15 to 30 oC) at 400 µmol mol-1 external CO2 concentration when grown at 15 oC, and in the shapes of the response curves when grown at 25 oC. The apparent activation energy of the maximum carboxylation rate of Rubisco differed substantially between cultivars at all growth temperatures, as well as changing with growth temperature in two of the cultivars. The activation energy ranged from 58 to 84 kJ mol-1, compared with the value of 64 kJ mol-1 used in many photosynthesis models. Much less variation in temperature responses occurred in photosynthesis measured at nearly saturating CO2 levels, suggesting more diversity in Rubisco than in electron transport thermal properties among these soybean cultivars.

scholarly journals Isolation of alkalophilic CGTase-producing bacteria and characterization of cyclodextrin-glycosyltransferase

2003 ◽  
Vol 46 (2) ◽  
pp. 183-186 ◽  
Author(s):  
lma Hiroko Higuti ◽  
Simone Wichert Grande ◽  
Roberta Sacco ◽  
Aguinaldo José do Nascimento
Keyword(s):  
Activation Energy ◽  
Enzyme Activity ◽  
Sugar Cane ◽  
Soil Samples ◽  
Optimum Temperature ◽  
Bacillus Firmus ◽  
Cyclodextrin Glycosyltransferase ◽  
Biochemical Tests ◽  
Starch Adsorption

One hundred and twenty five soil samples were collected from the regions of roots of corn, cassava, potato, bean, sugar cane, soya, and pumpkin. From these, 75 strains were isolated that produced a yellowish halo surrounding the colonies, due to a phenolphtalein-cyclodextrin (CD) complex, and these were selected as alkalophilic CGTase-producing bacteria. All the 75 strains were identified as Bacillus firmus by microscopy and biochemical tests. The activity of the CGTase's varied from 2² to 2(10) dilutions,when assayed by CD-trichloroethylene (TCE)-complex precipitation. Strain 31 that produced the enzyme at the higher level was selected, and its enzyme was partially purified by starch adsorption (x 17) in a yield of 51%. Maximum enzyme activity occurred at pH 5.5 and 8.5. At pH 5.5, the optimum temperature was 60°C. On increased from 30°C to 85°C, the thermodynamic parameter for activation energy was 8.27 kcal.mol-1. The enzyme was inhibited by Ca2+, Mg2+, Fe2+, Cu2+, Mn2+, and Zn2+.

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