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]

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]

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
References in periodicals archive ?
This analysis revealed that the conventional Michaelis constants were indeed dependent upon the concentration of the 'second' substrate.
It is noteworthy that in the presence of the allosteric interaction between two binding sites of substrates, the experimentally determined Michaelis constants should depend on the concentration of the second substrate.
The maximum velocity and apparent Michaelis constant for this reaction were approximately 342.2 units/g wet weight and 0.308 mM TAME, respectively, as determined by Lineweaver-Burk plot (Figure 2B).
The maximum velocity and apparent Michaelis constant for this reaction were approximately 0.804 units/g wet weight and 0.053 mM 4-NPC, respectively, as determined by Lineweaver-Burk plot (Figure 2C).
Though reports are limited in the literature for crustacea, the apparent Michaelis constant reported here (2.4-mg/ml starch) is similar to that (4.5 mg/ml) reported by Mayzaud (1985) for the copepod Acartia clausi.
Trypsin also demonstrated saturation kinetics and an apparent Michaelis constant of 0.31 mM TAME.