Heat and Photochemical Inactivations of Taka-Amylase A and Mechanisms of Protection by Substrate

1967 ◽  
Vol 22 (4) ◽  
pp. 403-406 ◽  
Author(s):  
Giiti Tomita
Keyword(s):  
Protective Action ◽  
Heat Inactivation ◽  
Thermodynamic Quantities ◽  
Combined Effects ◽  
Conformation Change ◽  
Enzyme Protein ◽  
Decomposition Products ◽  
Photochemical Processes ◽  
Enzyme Substrate ◽  
The Relationship

The heat, ultraviolet and riboflavin-sensitized visible inactivations of taka-amylase A are strongly inhibited by the presence of its substrate. The stabilization of the secondary structure of enzyme protein by the conformation change due to the formation of enzyme-substrate and -product complexes is responsible for the protection of enzyme from the heat inactivation. The photoinactivations are brought about by the combined effects of heat and photochemical processes. The observed protections from photoinactivations are due to the inhibition effects of substrate and its decomposition products on both processes. The thermodynamic quantities determined for the inactivation reactions throw some light on the relationship between the heat and photochemical processes, and on the mechanisms of the protective action of substrate.

Effects of Substrate on Heat Inactivation of Taka-amylase A

1967 ◽  
Vol 22 (3) ◽  
pp. 294-300 ◽  
Author(s):  
Giiti Tomita ◽  
Sam Soon Kim
Keyword(s):  
Protective Effect ◽  
Protective Action ◽  
Higher Order ◽  
The State ◽  
Heat Inactivation ◽  
Order Structure ◽  
Enzyme Protein ◽  
Enzyme Substrate ◽  
Hydrolysis Products ◽  
The Difference

Taka-amylase A is highly protected from heat inactivation and denaturation by the presence of its substrate, starch. The effect of pH on the protective action was studied to find the relation between the protective action and the state of ionization of taka-amylase A. The separation of protective effect of substrate from that of hydrolysis products was made by digesting starch with taka-amylase A before incubation to find the difference of protective abilities of substrate and hydrolysis products. The stabilization of the higher order structure of enzyme protein, depending on the state of ionization of enzyme protein, brought about by the formation of enzyme-substrate and -product complexes seems to be responsible for the appearance of the protective effect observed.

Protective Action and Risky Beliefs: The Relationship Between Religion and Gambling Fallacies

2021 ◽  
Author(s):  
Brenton M. Williams ◽  
Matthew Browne ◽  
Matthew Rockloff ◽  
George Stuart ◽  
Bradley P. Smith
Keyword(s):  
Protective Action ◽  
The Relationship

scholarly journals How College Students Assess the Threat of Infectious Diseases: Implications for University Leaders and Health Communicators

2021 ◽  
Vol 4 ◽  
pp. 129-164
Author(s):  
Yan Jin ◽  
Yen-I Lee ◽  
Brooke Fisher Liu ◽  
Lucinda Austin ◽  
Seoyeon Kim
Keyword(s):  
Infectious Disease ◽  
College Students ◽  
Online Survey ◽  
Protective Action ◽  
Sexually Transmitted ◽  
Wide Range ◽  
External Attribution ◽  
Action Taking ◽  
University Leaders ◽  
The Relationship

Higher education institutions and their students face a wide range of infectious disease threats (IDTs). However, there is a lack of theory-driven research on how to provide communication for multiple IDTs to motivate protective action taking. To close this gap, this study focuses on college students and two IDT types: respiratory and sexually transmitted infections. We tested an IDT appraisal model with data from an online survey conducted at two U.S. universities with 842 students. Findings indicate that IDT type led to different patterns of threat appraisal and protective action taking intentions. More specifically, participants perceived sexually transmitted threats as significantly more predictable and more controllable than respiratory threats. Participants also had higher intention to take protective action in response to respiratory threats than sexually-transmitted threats. We also found that external attribution-dependent (EAD) emotions (i.e., anger, sadness, surprise, and confusion) and an internal-attribution-dependent (IAD) emotion (i.e., hope) were sequential mediators in the relationship between IDT appraisal and protective action taking intentions for both infectious disease types. Implications for IDT communication research and practice are discussed.

scholarly journals Market concentration, corporate governance and innovation: Partial and combined effects in US-listed firms

2012 ◽  
Vol 1 (3) ◽  
pp. 199-215
Author(s):  
Mehmet Ugur ◽  
Nawar Hashem
Keyword(s):  
Corporate Governance ◽  
Robust Estimation ◽  
Market Concentration ◽  
Combined Effects ◽  
Cross Sectional ◽  
Book Value ◽  
Listed Firms ◽  
Innovation Research ◽  
Governance Indicators ◽  
The Relationship

Existing research on the relationship between market concentration and innovation has produced conflicting findings. In addition, the emerging literature on the relationship between corporate governance and innovation tends to focus only on partial effects of corporate governance on innovation. We aim to contribute to the debate by investigating both partial and combined effects of corporate governance and market concentration on innovation. Utilising a dataset for 1,400 non-financial US-listed companies and two-way cluster-robust estimation methodology, we report several findings. First, the relationship between market concentration and innovation is non-linear. Secondly, the relationship has a U-shape in the case of input measure of innovation (research and development - R&D – expenditures); but it has an inverted-U shape when net book-value of brands and patents is used as output measure of innovation. Third, corporate governance indicators such as anti-takeover defences and insider control tend to have a negative partial effect on R&D expenditures but a positive partial effect on net book-value of brands and patents. Finally, when interacted with market concentration, anti-takeover defences and insider control act as complements to market concentration. Hence, firms with strong anti-take-over defences and under insider control tend to spend more on R&D but are less able to generate valuable brands and patents as market concentration increases. These results are based on two-way cluster-robust estimation, which takes account of both serial and cross-sectional dependence in the error terms.

Cuando se tejen los sueños. La voz de la mujer sapara y su pueblo

2021 ◽  
pp. 91-94
Author(s):  
Rosita Ortega Vásquez
Keyword(s):  
Women's Rights ◽  
Protective Action ◽  
State Violence ◽  
Women’S Rights ◽  
Local Justice ◽  
Indigenous Organizations ◽  
Precautionary Measures ◽  
The Relationship

This article analyzes the relationship between the extractivist model in Ecuador and state violence against Amazonian women defenders based on the case of Nema Grefa, President of the Sapara Nation of Ecuador (NASE), who has been intimidated and threatened with death on several occasions. From the demand for protective action and request for precautionary measures in favor of the leader and the Sapara people. The analysis of this case discusses collective and women’s rights in a local justice scenario, where the articulation of indigenous organizations, organizations for the defense of women’s rights, ecofeminists and the Ombudsman’s Office (Defensoría del Pueblo) will be key.

Adsorption of surfactants at liquid/vapour and liquid/liquid interfaces

Surfactants ◽  
2019 ◽  
pp. 73-112
Author(s):  
Bob Aveyard
Keyword(s):  
Surfactant Concentration ◽  
Surface Concentration ◽  
Ionic Surfactants ◽  
Thermodynamic Quantities ◽  
Two Dimensional ◽  
Liquid Interfaces ◽  
Surfactant Mixtures ◽  
Surfactant Monolayers ◽  
Solvent Molecules ◽  
The Relationship

The variation of interfacial tension of a solution with surfactant concentration in bulk can be used, in conjunction with the Gibbs adsorption equation, to probe the behaviour of adsorbed surfactant monolayers. An adsorption isotherm equation expresses the relationship between bulk and surface concentrations of surfactant, and is used to determine thermodynamic quantities of surfactant adsorption. The variation of the surface pressure of a surfactant monolayer with the surface concentration is described by a surface equation of state, which reflects something of the nature of a monolayer. The way in which inorganic electrolytes modify the adsorption and monolayer behaviour of ionic surfactants is explained, and adsorption from surfactant mixtures is also introduced. In the Appendix, the discussion is extended to the treatment of adsorbed monolayers as two-dimensional solutions of surfactant with solvent molecules, rather than as two-dimensional gases.

Cooperative Binding of the Organophosphate Paraoxon to the (Na+ + K+)-ATPase

1995 ◽  
Vol 50 (9-10) ◽  
pp. 660-663 ◽  
Author(s):  
Janusz Blasiak
Keyword(s):  
Active Sites ◽  
Microsomal Fraction ◽  
Inhibitory Effect ◽  
Hill Coefficient ◽  
Cooperative Binding ◽  
Enzyme Protein ◽  
The Hill ◽  
The Relationship ◽  
Dose Dependent ◽  
Substrate Kinetics

Abstract Paraoxon. the main active metabolite of the organophosphorus insecticide parathion. exerted a dose-dependent inhibitory effect on the activity of pig kidney (Na+ + K+)-ATPase contained in microsomal fraction and purified from it. Substrate kinetics studies revealed the existence of two active sites with high and low affinity to ATP. The Dixon analysis of the mode of the inhibition indicated its noncompetitive character. The purified enzyme was more affected than enzyme contained in the microsomal fraction. The inhibition constant K, ranged from 73 to 246 μm depending on the type of preparation. The Hill coefficient (n) fulfilled the relationship 1<n<3. These properties of the interaction suggest the cooperative binding of paraoxon to the enzyme. An indirect mechanism of the interaction was proposed: paraoxon could inhibit the activity of the (N a+ + K+)-ATPase by excluding the enzyme protein from its normal lipid milieu

scholarly journals Does superoxide anion participate in 2-oxoglutarate-dependent hydroxylation?

1982 ◽  
Vol 205 (2) ◽  
pp. 339-344 ◽  
Author(s):  
Elisabeth Holme ◽  
Göran Lindstedt ◽  
Sven Lindstedt ◽  
Ingalill Nordin
Keyword(s):  
Superoxide Dismutase ◽  
Superoxide Anion ◽  
Potent Inhibitor ◽  
Enzymic Activity ◽  
Heat Inactivation ◽  
Low Molecular Weight ◽  
Enzyme Protein ◽  
Erythrocyte Superoxide Dismutase ◽  
Rule Out

The possible role of superoxide anion in 2-oxoglutarate-coupled dioxygenase reactions has been investigated. γ-Butyrobetaine hydroxylase (EC 1.14.11.1) was inhibited by human erythrocyte superoxide dismutase (EC 1.15.1.1), probably due to release of Cu2+ or Zn2+, as the inhibition was more pronounced after heat-inactivation of the dismutase and as Cu2+ was a potent inhibitor. Bovine superoxide dismutase and the Mn2+-containing superoxide dismutase from Escherichia coli were not inhibitory. Superoxide anion generated from xanthine/xanthine oxidase was not stimulatory and could not replace ascorbate. Thymine 7-hydroxylase (EC 1.14.11.6) and thymidine 2′-hydroxylase (EC 1.14.11.3) were not inhibited by erythrocyte superoxide dismutase or stimulated by superoxide anion. γ-Butyrobetaine hydroxylase was inhibited by a number of low-molecular-weight compounds, such as tetranitromethane, Nitro Blue Tetrazolium, adrenaline and Tiron, which may act as scavengers of superoxide anion. Involvement of this radical in other oxygenase reactions has been inferred from the findings that they were inhibitory for the respective enzymes. Several of these compounds also inhibited γ-butyrobetaine hydroxylase. It could be concluded from these experiments, however, that mechanisms other than disposal of superoxide anion might equally well be operative, such as hydrophobic interaction with the enzyme protein and interaction with compounds required for full enzymic activity, e.g. iron and ascorbate. The results appear to rule out a requirement for superoxide anion generated in free solution, and have not yielded evidence for participation of enzyme-bound superoxide anion in 2-oxoglutarate-dependent hydroxylations.

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