Michaelis


Michaelis constant An experimentally determined parameter inversely indicative of the affinity of an enzyme for its substrate. For a constant enzyme concentration, the Michaelis constant is that substrate concentration at which the rate of reaction is half its maximum rate. In general, the Michaelis constant is equivalent to the dissociation constant of the enzyme-substrate complex.  [c.262]

Km for an enzymatic reaction are of significant interest in the study of cellular chemistry. From equation 13.19 we see that Vmax provides a means for determining the rate constant 2- For enzymes that follow the mechanism shown in reaction 13.15, 2 is equivalent to the enzyme s turnover number, kcat- The turnover number is the maximum number of substrate molecules converted to product by a single active site on the enzyme, per unit time. Thus, the turnover number provides a direct indication of the catalytic efficiency of an enzyme s active site. The Michaelis constant, Km, is significant because it provides an estimate of the substrate s intracellular concentration.  [c.638]

Michaelis constant (p. 637) negatron (p. 642) neutron activation (p. 645) peristaltic pump (p. 652) positron (p. 642) quench (p. 634)  [c.658]

Michaelis-Arbuzov rearrangement  [c.632]

Ger. Offen. 3,705,386 (Sept. 1,1988), E. Michaelis and H. Hoch (to BASE).  [c.346]

Fig. 1. Free-energy profile for a kinetic resolution depicted by equation 1 that follows Michaelis-Menten kinetics. Fig. 1. Free-energy profile for a kinetic resolution depicted by equation 1 that follows Michaelis-Menten kinetics.
Since the El complex does not yield product P, and I competes with S for E, there is a state of competitive inhibition. By analogy to the Michaelis-Menten equation  [c.2149]

The biodegradation rate R is characterized by the Monod (or Michaelis-Menten) following relationship  [c.2193]

Michaelis constant (p. 637) negatron (p. 642) neutron activation (p. 645) peristaltic pump (p. 652) positron (p. 642) quench (p. 634)  [c.658]

Leonor Michaelis and Maud Menten laid the foundation for enzyme kinetics as early as 1913 by proposing the following scheme  [c.206]

The Michaelis-Menten scheme nicely explains why a maximum rate, V"max, is always observed when the substrate concentration is much higher than the enzyme concentration (Figure 11.1). Vmax is obtained when the enzyme is saturated with substrate. There are then no free enzyme molecules available to turn over additional substrate. Hence, the rate is constant, Vmax, and is independent of further increase in the substrate concentration.  [c.206]

Figure 11.1 A plot of the reaction rate as a function of the substrate concentration for an enzyme catalyzed reaction. Vmax is the maximal velocity. The Michaelis constant. Km, is the substrate concentration at half Vmax- The rate v is related to the substrate concentration, [S], by the Michaelis-Menten equation Figure 11.1 A plot of the reaction rate as a function of the substrate concentration for an enzyme catalyzed reaction. Vmax is the maximal velocity. The Michaelis constant. Km, is the substrate concentration at half Vmax- The rate v is related to the substrate concentration, [S], by the Michaelis-Menten equation
The Michaelis complex, ES, undergoes rearrangement to one or several transition states before product is formed. Energy is required for these rearrangements. The input energy required to bring free enzyme and substrate to the highest transition state of the ES complex is called the activation energy of the reaction (Figure 11.2). In the absence of enzyme, spontaneous conversion of substrate to product also proceeds through transition states that require activation energy. The rate of a chemical reaction is strictly dependent on its  [c.206]

Equation 1-108 can be considered as the Michaelis-Menten equation, where is the Michaelis constant and represented as  [c.24]

Figure 11-1a. Simple Michaelis-Menten kinetics. At low substrate concentration Figure 11-1a. Simple Michaelis-Menten kinetics. At low substrate concentration
Solving Equation 11-13 for the Michaelis constant gives  [c.837]

The Michaelis constant is equal to substrate concentration at which the rate of reaction is equal to one-half the maximum rate. The parameters and characterize the enzymatic reactions that are described by Michaelis-Menten kinetics. is dependent on total  [c.838]

Equation 11-15 is known as the Michaelis-Menten equation. It represents the kinetics of many simple enzyme-catalyzed reactions, which involve a single substrate. The interpretation of as an equilibrium constant is not universally valid, since the assumption that the reversible reaction as a fast equilibrium process often does not apply.  [c.839]

PARAMETERS IN THE MICHAELIS-MENTEN EQUATION  [c.839]

LINEARIZED FORM OF THE INTEGRATED MICHAELIS-MENTEN (MM) EQUATION  [c.843]

Perhaps the most exciting application of single-molecule teclmiques in biology is the probing of enzymatic reactions at the level of individual turnovers [192, 193], utilizing systems in which either enzyme or substrate or both undergo large changes in optical properties (e.g. switching from fluorescent to nonfluorescent states) during the course of the reaction. These studies allow the possibility of heterogeneity in reaction rates among nominally identical enzyme molecules to be assessed, and make it possible to probe memory effects, the extent to which an enzyme s binding constant or turnover rate depends upon its previous reaction history. Generally the enzyme is either bound to a surface [194] or confined within the pores of a gel [142] or nanoengineered stmcture [139, 143], and the substrate and product molecules allowed to diffuse toward and away from the immobilized enzyme. The catalytic activity among different molecules of nominally identical lactate dehydrogenase enzyme was found to vary by up to a factor of four, an observation tentatively attributed to the presence of multiple stable confonners of the enzyme [195]. A detailed study of single molecules of mammalian alkaline phosphatase revealed even more pronounced heterogeneities among different molecules (more than tenfold differences in turnover rate and more than two-fold differences in activation energy), which were attributed at least in part to post-translational modification producing chemically nonidentical enzyme molecules [196]. In contrast, single molecules of highly purified bacterial alkaline phosphatase have indistinguishable enzymatic activities [137]. Lengthy turnover trajectories of cholesterol oxidase, a flavoprotein that catalyses the oxidation of cholesterol by oxygen (figure Cl.5.17), have been analysed to obtain the distribution of on and off times in the Michaelis-Menten catalytic mechanism, and also revealed evidence for memory effects probably due to slow confonnational fluctuations in the protein [192, 193].  [c.2502]

Determining and Km for Enzyme-Catalyzed Reactions The value of Vm x and Km for an enzymatic reaction are of significant interest in the study of cellular chemistry. From equation 13.19 we see that Vmux provides a means for determining the rate constant /ca- For enzymes that follow the mechanism shown in reaction 13.15, /l2 is equivalent to the enzyme s turnover number, fccat- The turnover number is the maximum number of substrate molecules converted to product by a single active site on the enzyme, per unit time. Thus, the turnover number provides a direct indication of the catalytic efficiency of an enzyme s active site. The Michaelis constant, is significant because it provides an estimate of the substrate s intracellular concentration.  [c.638]

ARBUZOV MICHAELIS Phosphonale Synihesis Ni catalyzed phosphonate synthesis from phosphites and aryl halides Reaction of alkyl halides with phosphites proceeds without nickel salts  [c.5]

The Michaelis-Menten Equation 11-15 is not well suited for estimation of the kinetic parameters and Reananging Equation 11-15 gives various options for plotting and estimating the parameters.  [c.839]


See pages that mention the term Michaelis : [c.307]    [c.359]    [c.637]    [c.637]    [c.775]    [c.632]    [c.57]    [c.46]    [c.327]    [c.327]    [c.2138]    [c.2149]    [c.2149]    [c.637]    [c.637]    [c.775]    [c.5]    [c.261]    [c.261]    [c.128]   
Organic syntheses based on name reactions and unnamed reactions (1994) -- [ c.5 ]