Symbolism and terminology in enzyme kinetics. Recommendations 1981

doi:10.1042/bj2130561

Cited by 23 publications

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“…Therefore, K m is not one of the two basic properties. Changing from K m to A M , the Michaelis concentration, would be consistent with this interpretation [ 19 ].…”

Section: Discussionmentioning

confidence: 68%

“…The binding step is much faster than the conversion step, where the catalytic site converts the bound substrate to product and releases it. This is commonly assumed to involve a simple 1:1 stoichiometric relation between substrate bound and product released [ 19 ]. The binding rate constant for one mole of enzyme is defined here to be = κ 0 / E t = k cat / K m .…”

Section: Resultsmentioning

confidence: 99%

“…The binding rate constant for one mole of enzyme is defined here to be = κ 0 / E t = k cat / K m . The ratio, k cat / K m , is often referred to as the specificity constant [ 19 , 20 ]. Thus, k bind indicates the strength of the mutual interaction between a specific substrate and a specific enzyme, at the catalytic site, measured when A → 0.…”

Section: Resultsmentioning

confidence: 99%

“…The action of enzyme inhibitors offers additional perspective on interpreting K m = k cat / k bind . Consider five basic cases of enzyme inhibition: Competitive, Uncompetitive, Pure Non-Competitive, Predominantly Competitive, Predominantly Uncompetitive [ 19 ]. In no case does the inhibitor ( I ) cause the limiting rate, P sat , or the initial slope, κ 0 , of the observed data plot for the experimental system ( E t , I , A , P ) to increase .…”

Section: Discussionmentioning

confidence: 99%

“…The ratio of these observable empirical constants, P sat / κ 0 , defines K m . Thus, the mathematical analysis offers an operational definition of K m , independent of any interpretations [ 19 ]. This approach to defining K m is consistent with all the known factors.…”

Section: Discussionmentioning

confidence: 99%

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Saturation Behavior: a general relationship described by a simple second-order differential equation

Kepner¹

2010

Theor Biol Med Model

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BackgroundThe numerous natural phenomena that exhibit saturation behavior, e.g., ligand binding and enzyme kinetics, have been approached, to date, via empirical and particular analyses. This paper presents a mechanism-free, and assumption-free, second-order differential equation, designed only to describe a typical relationship between the variables governing these phenomena. It develops a mathematical model for this relation, based solely on the analysis of the typical experimental data plot and its saturation characteristics. Its utility complements the traditional empirical approaches.ResultsFor the general saturation curve, described in terms of its independent (x) and dependent (y) variables, a second-order differential equation is obtained that applies to any saturation phenomena. It shows that the driving factor for the basic saturation behavior is the probability of the interactive site being free, which is described quantitatively. Solving the equation relates the variables in terms of the two empirical constants common to all these phenomena, the initial slope of the data plot and the limiting value at saturation. A first-order differential equation for the slope emerged that led to the concept of the effective binding rate at the active site and its dependence on the calculable probability the interactive site is free. These results are illustrated using specific cases, including ligand binding and enzyme kinetics. This leads to a revised understanding of how to interpret the empirical constants, in terms of the variables pertinent to the phenomenon under study.ConclusionsThe second-order differential equation revealed the basic underlying relations that describe these saturation phenomena, and the basic mathematical properties of the standard experimental data plot. It was shown how to integrate this differential equation, and define the common basic properties of these phenomena. The results regarding the importance of the slope and the new perspectives on the empirical constants governing the behavior of these phenomena led to an alternative perspective on saturation behavior kinetics. Their essential commonality was revealed by this analysis, based on the second-order differential equation.

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“…Therefore, K m is not one of the two basic properties. Changing from K m to A M , the Michaelis concentration, would be consistent with this interpretation [ 19 ].…”

Section: Discussionmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 3 more Smart Citations

Saturation Behavior: a general relationship described by a simple second-order differential equation

Kepner¹

2010

Theor Biol Med Model

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Nomenclature

Powell¹

2005

Kirk-Othmer Encyclopedia of Chemical Technology

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Names for chemical substances have developed from terms based on their source, properties, or effects into an elaborate system in which names encode precise information about chemical structures. Nomenclature in inorganic chemistry developed first; it is primarily concerned with elemental composition and with ionic and oxidation states. Organic nomenclature at first followed the inorganic pattern, but diverged from it because of the importance of connectivity and isomerism in organic compounds. The present system of organic nomenclature is based on the principles of the Geneva Conference of 1892, developed and expanded by international conferences and commissions into the nomenclature recommended by the International Union of Pure and Applied Chemistry (IUPAC). The nomenclatures of inorganic, organic, and macromolecular chemistry and of biochemistry are in a continuing state of development; new recommendations from international bodies are published in appropriate journals, such as Pure and Applied Chemistry and Biochemistry. Rules and recommendations are collected in book form at intervals. Computer interactions with different aspects of nomenclature that began during the later years of the twentieth century have increased enormously during the last decade.

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Identification of CYP isozymes involved in benzbromarone metabolism in human liver microsomes

Kobayashi

Kajiwara

Ishikawa

et al. 2012

Biopharm & Drug Disp

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Benzbromarone (BBR) is metabolized to 1'-hydroxy BBR and 6-hydroxy BBR in the liver. 6-Hydroxy BBR is further metabolized to 5,6-dihydroxy BBR. The aim of this study was to identify the CYP isozymes involved in the metabolism of BBR to 1'-hydroxy BBR and 6-hydroxy BBR and in the metabolism of 6-hydroxy BBR to 5,6-dihydroxy BBR in human liver microsomes. Among 11 recombinant P450 isozymes examined, CYP3A4 showed the highest formation rate of 1'-hydroxy BBR. The formation rate of 1'-hydroxy BBR significantly correlated with testosterone 6β-hydroxylation activity in a panel of 12 human liver microsomes. The formation of 1'-hydroxy BBR was completely inhibited by ketoconazole in pooled human liver microsomes. On the other hand, the highest formation rate of 6-hydroxy BBR was found in recombinant CYP2C9. The highest correlation was observed between the formation rate of 6-hydroxy BBR and diclofenac 4'-hydroxylation activity in 12 human liver microsomes. The formation of 6-hydroxy BBR was inhibited by tienilic acid in pooled human liver microsomes. The formation of 5,6-dihydroxy BBR from 6-hydroxy BBR was catalysed by recombinant CYP2C9 and CYP1A2. The formation rate of 5,6-dihydroxy BBR was significantly correlated with diclofenac 4'-hydroxylation activity and phenacetin O-deethylation activity in 12 human liver microsomes. The formation of 5,6-dihydroxy BBR was inhibited with either tienilic acid or α-naphthoflavone in human liver microsomes. These results suggest that (i) the formation of 1'-hydroxy BBR and 6-hydroxy BBR is mainly catalysed by CYP3A4 and CYP2C9, respectively, and (ii) the formation of 5,6-dihydroxy BBR is catalysed by CYP2C9 and CYP1A2 in human liver microsomes.

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Symbolism and terminology in enzyme kinetics. Recommendations 1981

Cited by 23 publications

References 0 publications

Saturation Behavior: a general relationship described by a simple second-order differential equation

Saturation Behavior: a general relationship described by a simple second-order differential equation

Nomenclature

Identification of CYP isozymes involved in benzbromarone metabolism in human liver microsomes

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