Mi·chae·lis con·stant

(mi-kā'lis),

1. the true dissociation constant for the enzyme-substrate binary complex in a single-substrate rapid equilibrium enzyme-catalyzed reaction (usually symbolized by K_s);

2. the concentration of the substrate at which half the true maximum velocity of an enzyme-catalyzed reaction is achieved (when velocities are measured under initial rate and steady-state conditions); the ratio of rate constants (k₂ + k₃)/k₁ in the single-substrate enzyme-catalyzed reaction: E + S ⇄ ES ⇄ E + products, where E represents the free enzyme, S is the substrate, and ES is the central binary complex. The expression for the Michaelis constant will be more complex for multisubstrate reactions. An apparent Michaelis constant is a constant determined either under conditions that are not strictly steady-state and initial rate or under a condition that varies with the concentration of one or more cosubstrates.

Synonym(s): Michaelis-Menten constant

[Leonor Michaelis]

Farlex Partner Medical Dictionary © Farlex 2012

Mi·chae·lis con·stant

(mi-kā'lis kon'stănt)

1. The true dissociation constant for the enzyme-substrate binary complex in a single-substrate rapid equilibrium enzyme-catalyzed reaction (usually symbolized by K_s).

2. The concentration of the substrate at which half the true maximum velocity of an enzyme-catalyzed reaction is achieved.

[Leonor Michaelis]

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

Michaelis,

Leonor, German-U.S. chemist and physician, 1875-1949.

Michaelis buffer

Michaelis constant - the true dissociation constant for the enzyme-substrate binary complex in a single-substrate rapid equilibrium enzyme-catalyzed reaction. Synonym(s): Michaelis-Menten constant

Michaelis-Gutmann body - a rounded homogenous body containing calcium and iron found within macrophages in the bladder wall in malacoplakia.

Michaelis-Menten constant - Synonym(s): Michaelis constant

Michaelis-Menten equation - an initial-rate equation for a single-substrate noncooperative enzyme-catalyzed reaction relating the initial velocity to the initial substrate concentration. Synonym(s): Victor-Michaelis-Menten equation

Michaelis-Menten hypothesis - that a complex is formed between an enzyme and its substrate (the O'Sullivan-Tompson hypothesis), which complex then decomposes to yield free enzyme and the reaction products (Brown hypothesis), the latter rate determining the overall rate of substrate-product conversion.

Victor-Michaelis-Menten equation - Synonym(s): Michaelis-Menten equation

Medical Eponyms © Farlex 2012

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References in periodicals archive

The effect of the inhibition is considered with Michaelis-Menten kinetics with Michaelis-Menten constant [ED.sub.50] (called the median effective dose [22]) resulting in the velocity term [x.sub.1][x.sub.3]/([ED.sub.50] + [x.sub.3]).

Modeling of Tumor Growth Incorporating the Effects of Necrosis and the Effect of Bevacizumab

The study of reaction rates was directly proportional to ChE concentration across the range of dilutions tested confirming that Michaelis-Menten kinetics was supported in this range (Figures 5(a)-5(d)).

A method for fast assessment of OP/CB exposure in the Japanese quail (Coturnix coturnix japonica) using combined esterases enzyme activity as biomarkers

[4.] Bardsley, WG, Leff, P, Kavanagh, J and Waight, RD, "Deviations from Michaelis-Menten kinetics. The possibility of complicated curves for simple kinetic schemes and the computer fitting of experimental data for acetylcholinesterase, acid phosphatase, adenosine deaminase, arylsulphatase, benzylamine oxidase, chymotrypsin, fumarase, galactose dehydrogenase, [beta]-galactosidase, lactate dehydrogenase, peroxidase and xanthine oxidase", Biochemical Journal 1980; 187: 739-765.

Confidence bands for rational rate equations

Discrimination among eight modified Michaelis-Menten kinetics models of cellulose hydrolysis with a large range of substrate/enzyme ratios.

Hidrolisis enzimatica de residuos de la cosecha de cana de azucar

First, Michaelis-Menten kinetics are an approximation (Bardsley et al.

A mechanistic modeling framework for predicting metabolic interactions in complex mixtures

In the cases when the Michaelis-Menten kinetics or the random-order mechanism were used the mean values of [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] for all bi-substrate (1:1) systems were in the range of 58-88% of the assumed additive values.

Biodegradability of phenol, resorcinol and 5-methylresorcinol as single and mixed substrates by activated sludge

So endoglucanase obeys Michaelis-Menten kinetics (Figs.

Digestive Cellulose Hydrolyzing Enzyme Activity (endo- b-1, 4- D-glucanase) in the Gut and Salivary Glands of Blister Beetle, Mylabris pustulata

This fact shows that the reactions exhibit 1 to zero order kinetics with respect to all diols indicating Michaelis-Menten kinetics.

Kinetics of phosphotungstic acid catalyzed oxidation of propan-1,3-diol and butan-1,4-diol by N-chlorosaccharin

"When Sunneybegan these researches in the late '90s, people said, 'Gee, if you have these fluctuating rates, how come we almost always see Michaelis-Menten kinetics? Something must be wrong with your experiment,'" recalls Attila Szabo of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Md.

Enzymes exposed: clearer views of the cell's movers and shakers threaten a century-old mainstay of biology

In contrast to Michaelis-Menten kinetics, which is used to describe a process catalyzed by a single enzyme, Monod kinetics describes processes (both growth and growthlinked biodegradation) of a more complex nature in which many enzyme systems are involved.

Modelling of chloride influence upon activated sludge community growth/Chloridu itakos veikliojo dumblo biocenozes dinamikai modeliavimas