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Substrate (chemistry)

About: Substrate (chemistry) is a research topic. Over the lifetime, 35902 publications have been published within this topic receiving 740722 citations. The topic is also known as: enzyme substrate.


Papers
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Journal ArticleDOI
TL;DR: From the kinetic data, it becomes evident that the reductive amination reaction is highly adaptive to the ammonium environment.

14,480 citations

Book
01 Jan 1979
TL;DR: Basic Principles of Chemical Kinetics Introduction to Enzyme Kinetics "Alternative" Enzymes Practical Aspects of Kinetics Deriving Steady-state Rate Equations Reversible Inhibition and Activation Tight-binding and Irreversible Inhibitors
Abstract: Basic Principles of Chemical Kinetics Introduction to Enzyme Kinetics "Alternative" Enzymes Practical Aspects of Kinetics Deriving Steady-state Rate Equations Reversible Inhibition and Activation Tight-binding and Irreversible Inhibitors Reactions of More than One Substrate Use of Isotopes for Studying Enzyme Mechanisms Effect of pH on Enzyme Activity Temperature Effects on Enzyme Activity Regulation of Enzyme Activity Multienzyme Systems Fast Reactions Estimation of Kinetic Constants Standards for Reporting Enzymology Data Solutions and Notes to Problems Index

2,220 citations

Book ChapterDOI
TL;DR: This chapter provides the spectrophotometric, titrimetric, nitrite, and cyanide assay for the differentiation of glutathione S-transferases.
Abstract: Publisher Summary This chapter provides the spectrophotometric, titrimetric, nitrite, and cyanide assay for the differentiation of glutathione S-transferases. Spectrophotometric assays depend upon a direct change in the absorbance of the substrate when it is conjugated with glutathione (GSH). Because each of the reactions is catalyzed at a finite rate in the absence of enzyme, care is needed to reduce nonenzymatic catalysis by minimizing substrate concentrations and by decreasing pH wherever necessary. Titrimetric assay is based on the principle that the conjugation of alkyl halides with GSH can be measured titrimetrically. Although acid production accompanies many of the transferase catalyzed reactions in which thioethers are formed, titrimetry is only used when more convenient assays are not available. Nitrite assay is based on the principle that nitrite is released when GSH reacts with nitroalkanes or with organic nitrate esters. The nitrite can be assayed as the limiting factor in a diazotization reaction with sulfanilamide that produces a readily quantitatable pink dye. Cyanide assay is based on the fact that when glutathione transferases catalyze the attack of the glutathione thiolate ion on the electrophilic sulfur atom of several organic thiocyanates, it results in the formation of an asymmetric glutathionyl disulfide and cyanide. Cyanide can be readily quantitated by a calorimetric method.

2,074 citations

Journal ArticleDOI
Jens Chr. Skou1
TL;DR: Leg nerves from the shore crab contain an adenosine triphosphatase which is located in the submicroscopic particles, and the influence of sodium, potassium, magnesium and calcium ions on this enzyme has been investigated.
Abstract: Leg nerves from the shore crab (Carcinus maenas) contain an adenosine triphosphatase which is located in the submicroscopic particles. The influence of sodium, potassium, magnesium and calcium ions on this enzyme has been investigated. The presence of magnesium ions is an obligatory requirement for the activity of the enzyme. Sodium ions increase the activity when magnesium ions are present. Potassium ions increase the activity when the system contains both magnesium and sodium ions. Potassium ions in high concentration inhibit that part of the activity which is due to Na+, while the activity due to Mg++ is not affected. Calcium ions inhibit the enzyme under all conditions. When Mg++ or Mg++ + Na+ are present in the system, the optimum magnesium concentration is equal to the concentration of ATP. If potassium ions are added, the optimum magnesium concentration is doubled. If calcium ions are also added, the optimum magnesium concentration becomes still higher, and it increases with the calcium concentration. A majority of these observations may be explained by assuming (a) that the substrate most readily attacked by the enzyme is sodium-magnesium-ATP, (b) that potassium ions stimulate the enzyme directly, and (c) that an increase in the concentration of potassium ions leads to a displacement of sodium ions from the substrate and accordingly to an inhibition of the reaction. If the system contains the four cations in concentrations roughly equal to those in the crab-nerve axoplasm, an increase in the sodium concentration as well as a decrease in the potassium concentration will lead to an intensification of the enzyme activity. This observation, as well as some other characteristics of the system, suggest that the adenosine triphosphatase studied here may be involved in the active extrusion of sodium from the nerve fibre.

1,800 citations

Journal ArticleDOI
Jens Chr. Skou1
TL;DR: In this article, the authors investigated the influence of different cations on the activity of an adenosine triphosphatase (ATP) enzyme in the leg nerves of crabs.

1,747 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202214
2021807
20201,053
20191,064
20181,112
20171,024