Michaelis-Menten parameter

For any arbitrary metabolic network, the Jacobian matrix can be decomposed into a sum of three fundamental contributions A term M eg that relates to allosteric regulation. A term M in that relates to the kinetic properties of the network, as specified by the dissociation and Michaelis Menten parameters. And, finally, a term that relates to the displacement from thermodynamic equilibrium. We briefly evaluate each contribution separately. 

Table 6.2 Effect of hypoxia on Michaelis-Menten parameters for NH4+ absorption by rice. Plants were grown in nutrient solutions containing IOOP.MNH4, aerated for 21 days and then exposed to hypoxia for 7 days...

In order to use PBTK modeling in the assessment of mixtures, Cassee et al. (1998) suggest that one of the components is first modeled and regarded as the prime toxicant being modified by the other components. Based on in vitro data on the other components, effects of, e.g., inhibition or induction of specific biotransformation isoenzymes can be incorporated in the model. Effects of competition between chemicals in a mixture for the same biotransformation enzymes may also be incorporated by translating the effects into effects on the Michaelis-Menten parameters that are then incorporated into the model. 

E]0 = 5xl0-4 mmol/m3 and substrate concentration [S]D = 40 rrmol/m3. The Michaelis-Menten parameters for this reaction are Vg = 0.65 irenol m-3 s-1,... 

Example 3.10.2 Approximate D - optimal design for estimating Michaelis-Menten parameters... 

The rate of butadiene metabolism in diverse cell fractions has been investigated in various species and is characterized by the Michaelis-Menten parameters and apparent Three methods have been used to determine these parameters ... 

Table 17.7 Apparent Michaelis-Menten Parameters Reported for Microbial Degradation of Various Substrates...

The rate constant for the formation of product from a particular substrate. kcat is obtained by dividing the Michaelis-Menten parameter, Vmax, by the total enzyme concentration. In real terms, the constant is a measure of how rapidly an enzyme can operate once its active site is occupied. 

The Monod kinetic parameters, and Ks, cannot be estimated with a series of batch runs as easily as the Michaelis-Menten parameters for an enzyme reaction. In the case of an enzyme reaction, the initial rate of reaction can be measured as a function of substrate concentration in batch runs. However, in the case of cell cultivation, the initial rate of reaction in a batch run is always zero due to the presence of a lag phase, during which Monod kinetics does not apply. It should be noted that even though the Monod equation has the same form as the Michaelis-Menten equation, the rate equation is different. In the Michaelis-Menten equation,... 

The Michaelis-Menten equation can also be rearranged to give Equation 11.15, the Eadie-Hofstee equation, and the rate data plotted according to this, as shown in Fig. 11.1 IB, give a better graphical estimation of the Michaelis-Menten parameters than does the... 

In another report, Michaelis-Menten parameters of ALP have been obtained using a one-shot Lineweaver-Burk (reciprocal) plot. This can be achieved by simultaneously measuring the conversion of 12 independent concentrations of the substrate (4-methylumbelliferyl phosphate) created on-chip. The enzyme was streptavidin-conjugated ALP that was linked to biotinylated phospholipid bilayers coated inside PDMS microchannels. The blue fluorescence of the enzymatic product, 7-hydroxy-4-methyl coumarin, was measured [ 1043]. The surface-bound enzyme was found to have a lower (sixfold) turnover rate than the free enzyme in solutions. After diffusion mixing between two streams (substrate and buffer)... 

Membrane vesicles, prepared from CHO cells, have been used to determine the kinetic parameters associated with P-gp efflux (97,98). Factors such as the ATP hydrolysis rate associated with transport of various substrates have been studied along with the Michaelis-Menten parameters of efflux for various substrates. 

Determine the Michaelis-Menten Parameters Vmax and Km for the reaction ... 

In this case the Michaelis-Menten parameters are Km = k-i/k+i, which is the dissociation constant, and Vmax = k+2E0. Here we have arrived at the familiar Michaelis-Menten result without making the assumption that the substrate concentration [S] is in excess of the enzyme concentration. Recall that the quasi-steady... 

Table 17.4 Examples of Michaelis-Menten parameters of DIN uptake for upwelling areas...

Reversible inhibition that produces complete loss of catalytic activity is referred to as linear inhibition because the plots of K IV or 1/y versus [I] are straight lines. When some catalytic activity remains, even at saturating amounts of inhibitor, it is referred to as hyperbohc inhibition because these plots are nonlinear (this case will not be considered here). Both of these types of reversible inhibition are further classified according to the various apparent Michaelis-Menten parameters that are affected by the inhibitor. The two limiting cases are competitive inhibition and uncompetitive inhibition a third type is mixed inhibition, which includes as a special case noncompetitive inhibition. 

Example 7-7 Evaluation of Michaelis-Menten Parameters Vmax mid K ... 

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