Équation de Michaelis-Menten

L’équation de Michaelis-Menten (ou de Michaelis-Menten-Henri) permet de décrire la cinétique d'une réaction catalysée par une enzyme agissant sur un substrat unique pour donner irréversiblement un produit. Elle relie la vitesse stationnaire initiale de la réaction à la concentration initiale en substrat et à des paramètres caractéristiques de l'enzyme. L'équation décrit un comportement cinétique très classique, observé avec de nombreuses enzymes, mais elle ne permet pas de rendre compte de certains comportements complexes, comme ceux résultant de l'existence de plusieurs sites actifs qui interagissent , ni de comprendre les propriétés cinétiques d'enzymes qui catalysent une réaction faisant intervenir plusieurs substrats. L'équation n'est pas valable si la réaction est catalysée de façon réversible et que le produit de la réaction est présent . Formule et représentation vignette|Représentation de la loi de vitesse de Michaelis–Menten, montrant la vitesse initiale de la r

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (56)

Publications associées

Chargement

Personnes associées (5)

Personnes associées

Chargement

Unités associées (3)

Unités associées

Chargement

Concepts associés (25)

Concepts associés

Chargement

Cours associés (33)

Cours associés

Chargement

Séances de cours associées (97)

Séances de cours associées

Chargement

Quantification of biodegradation for o-xylene and naphthalene using first order decay models, Michaelis-Menten kinetics and stable carbon isotopes

At a former wood preservation plant severely contaminated with coal tar oil, in situ bulk attenuation and biodegradation rate constants for several monoaromatic (BTEX) and polyaromatic hydrocarbons (PAH) were determined using (1) classical first order decay models, (2) Michaelis-Menten degradation kinetics (MM), and (3) stable carbon isotopes, for o-xylene and naphthalene. The first order bulk attenuation rate constant for o-xylene was calculated to be 0.0025 d(-1) and a novel stable isotope-based first order model, which also accounted for the respective redox conditions, resulted in a slightly smaller biodegradation rate constant of 0.0019 d(-1). Based on MM-kinetics, the o-xylene concentration decreased with a maximum rate of k(max)=0.1 mu g/L/d. The bulk attenuation rate constant of naphthalene retrieved from the classical first order decay model was 0.0038 d(-1). The stable isotope-based biodegradation rate constant of 0.0027 d(-1) was smaller in the reduced zone, while residual naphthalene in the oxic part of the plume further downgradient was degraded at a higher rate of 0.0038 d(-1). With MM-kinetics a maximum degradation rate of k(max)=12 mu g/L/d was determined. Although best fits were obtained by MM-kinetics, we consider the carbon stable isotope-based approach more appropriate as it is specific for biodegradation (not overall attenuation) and at the same time accounts for the dominant electron-accepting process. For o-xylene a field based isotope enrichment factor epsilon(field) of - 1.4 could be determined using the Rayleigh model, which closely matched values from laboratory studies of o-xylene degradation under sulfate-reducing conditions. (C) 2008 Elsevier B.V. All rights reserved.

2009

Chargement

Thermodynamic and kinetic degradation reactions of organic substances in groundwater modelled with PHREEQC

Johann Jakob Holch

Aim of this diploma thesis is to approach to kinetic modelling of subsurface hydrochemistry with the program code phreeqc. The reaction considered is the degradation of organic mass and its concomitant reactions. Phreeqc is a program for thermodynamical based equilibrium calculations of geo- and hydrochemistry. Although the degradation of organic matter, and the associated reduction reactions due to the oxidation of organic matter, can be modelled with phreeqc, it does not account for kinetically controlled reactions, whose characteristic feature is the dependency of time. This study focuses on the state of the art of environmental modelling, the thermodynamical based calculation of the degradation of organic matter and on two mathematical approaches to model bacterial degradation of a contaminant, the Monod equation and the Michaelis-Menten approach. Sensitivity analyses of the respective models runs were done. As a result one can see, that the redox chemistry of a natural water depends strongly on the abundance of oxygen and nitrate and, as a matter of course, on the abundance of organic matter. Considering bacterial activity within the degradation process, two basic mathematical formulations have been stated. The Monod equation and the Michaelis-Menten formulation were implemented in a BASIC interpreter in PHREEQC. The sensitivity analyses show, that that a accurate determination of the parameters in laboratory or field is essential. The coupling of kinetically controlled reactions and thermodynamical based equilibrium calculations might lead to auspicious hydrochemical modelling capabilities.

2008

Chargement

Real-time monitoring of single-cell secretion with a high-throughput nanoplasmonic microarray

Hatice Altug, Saeid Ansaryan, Xiaokang Li, Yen-Cheng Liu, Eduardo Romero Arvelo

Proteins secreted by cells play significant roles in mediating many physiological, developmental, and pathological processes due to their functions in intra/intercellular communication and signaling. Conventional end-point methods are insufficient for understanding the temporal response in cell secretion process, which is often highly dynamic. Furthermore, cellular heterogeneity makes it essential to analyze secretory proteins from single cells. To uncover individual cellular activities and the underlying kinetics, new technologies are needed for real-time analysis of the secretomes of many cells at single-cell resolution. This study reports a high-throughput biosensing microarray platform, which is capable of label-free and real-time secretome monitoring from a large number of living single cells using a biochip integrating ultrasensitive nanoplasmonic substrate and microwell compartments having volumes of ∼0.4 nL. Precise synchronization of image acquisition and microscope stage movement of the developed optical platform enables spectroscopic analysis with high temporal and spectral resolution. In addition, our system allows simultaneous optical imaging of cells to track morphology changes for a comprehensive understanding of cellular behavior. We demonstrated the platform performance by detecting interleukin-2 secretion from hundreds of single lymphoma cells in real-time over many hours. Significantly, the analysis of the secretion kinetics allows us to study cellular response to the stimulations in a statistical way. The new platform is a promising tool for the characterization of single-cell functionalities given its versatility, throughput and label-free configuration.

2022

Chargement

Cinétique enzymatique

La cinétique enzymatique a pour objet d'identifier et de décrire les mécanismes des réactions biochimiques, catalysées par les enzymes (réaction enzymatique), en étudiant leur vitesse c'est-à-dire

Enzyme

redresse=1.5|vignette| Représentation d'une α-glucosidase () avec à sa droite le substrat au-dessus des produits de réaction . redresse=1.5|vignette|Diagramme d'une réaction catalysée montrant l'éner

Glucose

Les glucoses sont des sucres de formule brute . Le mot « glucose » provient du grec ancien τὸ γλεῦκος / gleukos qui désignait les vins doux ou liquoreux, voire le moût. Le suffixe -ose est un classi

ChE-403: Heterogenous reaction engineering

The theoretical background and practical aspects of heterogeneous reactions including the basic knowledge of heterogeneous catalysis are introduced. The fundamentals are given to allow for the use of chemical reactors to study reaction kinetics and test various mechanistic assumptions.

CH-313: Chemical biology

Closely interfacing with bioengineering and medicine, this course provides foundational concepts in applying small-molecule chemical toolsets to probe the functions of living systems at the mechanistic and molecular level with emphasis placed on quantitative understanding and improving human health.

CH-310: Dynamics and kinetics

The course covers the principles of chemical kinetics, including differential rate laws, derivation of exact and approximate integral rate laws for common elementary and composite reactions, fundamentals of collision and transition state theories, and applications such as enzymatic catalysis.