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Journal ArticleDOI

The Determination of Enzyme Dissociation Constants

01 Mar 1934-Journal of the American Chemical Society (American Chemical Society)-Vol. 56, Iss: 3, pp 658-666
TL;DR: On the basis of the assumed theory the rate of the observed reaction is directly proportional to the concentration of the enzyme-substrate compound, where (E:l = (ES).
Abstract: On the basis of the assumed theory the rate of the observed reaction is directly proportional to the concentration of the enzyme-substrate compound, (ES), a t all values of the concentration of the substrate, (S). It is proportional to (S) only a t low values of (S). The numerical value of the dissociation constant is given by the substrate concentration a t half-maximum velocity, where (E:l = (ES). The equilibrium in equation 1 may be heterogeneous or homogeneous. Hitchcock'\" has pointed
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Journal ArticleDOI
TL;DR: Glutathione peroxidase activity is found to be associated with a relatively stable, nondialyzable, heat-labile, intracellular component which is separable from hemoglobin, by gel filtration and ammonium sulfate precipitation.

10,439 citations

Journal ArticleDOI
TL;DR: The median-effect principle and its mass-action law based computer software are gaining increased applications in biomedical sciences, from how to effectively evaluate a single compound or entity to how to beneficially use multiple drugs or modalities in combination therapies.
Abstract: The median-effect equation derived from the mass-action law principle at equilibrium-steady state via mathematical induction and deduction for different reaction sequences and mechanisms and different types of inhibition has been shown to be the unified theory for the Michaelis-Menten equation, Hill equation, Henderson-Hasselbalch equation, and Scatchard equation. It is shown that dose and effect are interchangeable via defined parameters. This general equation for the single drug effect has been extended to the multiple drug effect equation for n drugs. These equations provide the theoretical basis for the combination index (CI)-isobologram equation that allows quantitative determination of drug interactions, where CI 1 indicate synergism, additive effect, and antagonism, respectively. Based on these algorithms, computer software has been developed to allow automated simulation of synergism and antagonism at all dose or effect levels. It displays the dose-effect curve, median-effect plot, combination index plot, isobologram, dose-reduction index plot, and polygonogram for in vitro or in vivo studies. This theoretical development, experimental design, and computerized data analysis have facilitated dose-effect analysis for single drug evaluation or carcinogen and radiation risk assessment, as well as for drug or other entity combinations in a vast field of disciplines of biomedical sciences. In this review, selected examples of applications are given, and step-by-step examples of experimental designs and real data analysis are also illustrated. The merging of the mass-action law principle with mathematical induction-deduction has been proven to be a unique and effective scientific method for general theory development. The median-effect principle and its mass-action law based computer software are gaining increased applications in biomedical sciences, from how to effectively evaluate a single compound or entity to how to beneficially use multiple drugs or modalities in combination therapies.

4,270 citations


Cites background from "The Determination of Enzyme Dissoci..."

  • ...Note that competitiveness can be determined by the Lineweaver-Burk plot (Lineweaver and Burk, 1934) plot, whereas exclusiveness can be determined by the median-effect (Chou, 1976) plot....

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  • ...Competitiveness can be determined by the Lineweaver-Burk plot (Lineweaver and Burk, 1934), and exclusivity can be determined by the median-effect plot (Chou, 1976)....

    [...]

Journal ArticleDOI
TL;DR: Compounds Used-N”l-Acetyl-n-ornithine was synthesized as previously described and L-Ornithine monohydrochloride was obtained from the Mann Research Laboratories.

4,028 citations

Book ChapterDOI
TL;DR: Two methods are described for the catalase assay by disappearance of peroxide are: ultraviolet spectrophotometry and permanganate titration and indirect measurements of the decrease of light absorption caused by the decomposition of hydrogen peroxide byCatalase.
Abstract: Publisher Summary This chapter discusses the assay of catalases and peroxidases are: (1) catalase assay by disappearance of peroxide; (2) method for crude cell extracts; (3) direct spectrophotometric assay of catalase and peroxidase in cells and tissues; and (4) peroxidase assay by spectrophotometric measurements of the disappearance of hydrogen donor or the appearance of their colored oxidation products. Two methods are described for the catalase assay by disappearance of peroxide are: ultraviolet spectrophotometry and permanganate titration. Ultraviolet spectrophotometryis a method devised, on the basis of the absorption curves for peroxide solutions, for determining the activity of catalase by direct measurements of the decrease of light absorption in the region 230 to 250 mμ caused by the decomposition of hydrogen peroxide by catalase. In the case of method for crude cell extracts, oxygen evolution caused by the decomposition of hydrogen peroxide is measured with the conventional manometric technique. Peroxidase assay by spectrophotometric measurements of the disappearance of hydrogen donor or the appearance of their colored oxidation products includes the guaiacol test and the pyrogallol test.

3,917 citations

Journal ArticleDOI
TL;DR: Preliminary studies indicate that benzoyl dl -arginine p -nitroanilide hydrochloride is also hydrolyzed by papain, and that of l -LPA is in a more alkaline region than normally found for trypsin substrates.

3,118 citations