Michaelis constant

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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 Ks);
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.
[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 Ks).
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
References in periodicals archive ?
In Section 2, a brief description of Michaelis-Menten kinetics and its equation is given.
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]).
From Figure 6(b), it was observed that the response current increased with the increase of catechol concentration at low catechol concentration and at high concentration the current increased slowly and tended to stable when the concentration of catechol was high enough, which indicated the characteristic of Michaelis-Menten kinetics. As observed in Figure 6(b), the linear ranges of Mg-MCM41/PVA/Lac/Au and MCM-41/PVA/Lac/Au electrode were from 0.94 to 10.23 [micro]M and 0.46 to 4.01 [micro]M, and the sensitivities were 16.92 A/M and 12.61 A/M, respectively.
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)).
[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.
Discrimination among eight modified Michaelis-Menten kinetics models of cellulose hydrolysis with a large range of substrate/enzyme ratios.
First, Michaelis-Menten kinetics are an approximation (Bardsley et al.
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.
This fact shows that the reactions exhibit 1 to zero order kinetics with respect to all diols indicating Michaelis-Menten kinetics.
"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.
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.