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Total enzyme concentration

Equation 1-106 predicts that the initial rate will be proportional to the initial enzyme concentration, if the initial substrate concentration is held constant. If the initial enzyme concentration is held constant, then the initial rate will be proportional to the substrate concentration at low substrate concentrations and independent of the substrate concentration at high substrate levels. The maximum reaction rate for a given total enzyme concentration is... [Pg.24]

Overall enzyme balance and equilibrium constants are defined for the intermediate substrate and enzyme complex. The total enzyme concentration is the sum of free and conjugated enzymes with the substrates. [Pg.100]

The initial and total enzyme concentrations are defined based on measurable components given below ... [Pg.100]

The total enzyme concentration is the sum of free and conjugated enzymes with substrates. [Pg.102]

From the equilibrium constant, the free enzyme concentration must be defined. We know the total enzyme concentration as the sum of the conjugated enzymes with substrates and the free enzymes. [Pg.103]

If [E]t is used to represent the total enzyme concentration, then [E]ss Thus Eq. (4-111) can be rearranged as... [Pg.92]

Reaction 1 is the slowest step in this series of reactions leading to product formation. It is the rate-limiting step. Since this reaction involves bringing E and S together, it is a second-order reaction overall and first order with respect to the total enzyme concentration and the substrate concentration. [Pg.100]

Because enzyme, substrate and product are all in the same medium we can conveniently work with concentrations. With the total enzyme concentration equal to [EJtot, the conservation of active species requires that... [Pg.75]

Figure 7.2 Measured IC50 value as a function of total enzyme concentration for (A) an inhibitor displaying a ATfpp value of 5 nM, reflecting the behavior of an inhibitor in Strauss and Goldstein s zone B, and (B) another inhibitor displaying a K ff of 5 lM, reflecting the behavior of an inhibitor in Strauss and Goldstein s zone A. Figure 7.2 Measured IC50 value as a function of total enzyme concentration for (A) an inhibitor displaying a ATfpp value of 5 nM, reflecting the behavior of an inhibitor in Strauss and Goldstein s zone B, and (B) another inhibitor displaying a K ff of 5 lM, reflecting the behavior of an inhibitor in Strauss and Goldstein s zone A.
Here m is the slope value and [ii]app is the apparent total enzyme concentration, typically estimated from protein assays and other methods (Copeland, 1994). Note from Equation (7.13) that when our estimate of enzyme concentration is incorrect, the slope of the best fit line of IC50 as a function of [E] will not be 1/2, as theoretically expected. Nevertheless, the v-intercept estimate of K pp is unaffected by inaccuracies in [ ]. In fact we can combine Equations (7.12) and (7.13) to provide an accurate determination of [ /]T from the slope of plots such as those shown in Figure 7.2. The true value of [ii]T is related to the apparent value [ TPP as... [Pg.184]

The next question to be addressed is what the maximum concentration of inhibitor should be at the start of the 1.5-fold dilution series. Murphy suggests starting the dilution series at a concentration of inhibitor equal to 30[ ]T (or more correctly 30 times ones best estimate of total enzyme concentration). Simulations suggest that this dilution scheme will provide adequate data points within region B for inhibitors with potencies ranging from A fpp/[ ]T = 0.01 to 10. [Pg.188]

Use of Morrison s quadratic equation, together with Murphy s recommended dilution scheme, will allow accurate estimates of Kfpjpj as low as 100-fold below the total enzyme concentration. Based on Murphy s simulations, the most accurate determination of Kfpp is obtained for inhibitor titrations performed at / T = 10A I, (Murphy, 2004). [Pg.188]

Thus, by either titrating tight binding inhibitor concentration at a high, fixed enzyme concentration, and vice versa, one can obtain highly accurate estimates of the total enzyme concentration in a sample. These methods are commonly used to... [Pg.210]

If the conservation equation for total enzyme concentration (7.3.25) is employed, the last equation becomes... [Pg.229]

The total enzyme concentration is the sum of the concentrations of the free and bound forms, E and AE, and the ratio of the latter values depends only on the substrate concentration and the three rate constants in 17.17. From these observations, it follows that for an enzymatically promoted kinetic reaction k,... [Pg.251]

Moreover the total enzyme concentration is taken constant, CE = CES + CE. For... [Pg.852]

Aiming at a computer-based description of cellular metabolism, we briefly summarize some characteristic rate equations associated with competitive and allosteric regulation. Starting with irreversible Michaelis Menten kinetics, the most common types of feedback inhibition are depicted in Fig. 9. Allowing all possible associations between the enzyme and the inhibitor shown in Fig. 9, the total enzyme concentration Er can be expressed as... [Pg.139]

Note that written in this form Eq. (106) retains the linear dependency of the rate on the total enzyme concentration Ej, typical for most Michaelis Menten mechanisms. The dependence on the substrate concentrations is approximated by a sum of nonlinear logarithmic terms [85, 86, 318, 320],... [Pg.184]

Comparing with Eq. (44) and using the rapid equilibrium assumption with dissociation constants K, the total enzyme concentration can be written as... [Pg.186]

In the equations describing enzyme kinetics in this chapter, the notation varies a bit from other chapters. Thus v is accepted in the biochemical literature as the symbol for reaction rate while Vmax is used for the maximum rate. Furthermore, for simplification frequently Vmax is truncated to V in complex formulas (see Equations 11.28 and 11.29). Although at first glance inconsistent, these symbols are familiar to students of biochemistry and related areas. The square brackets indicate concentrations. Vmax expresses the upper limit of the rate of the enzyme reaction. It is the product of the rate constant k3, also called the turnover number, and the total enzyme concentration, [E]o. The case u, = Vmax corresponds to complete saturation of all active sites. The other kinetic limit, = (Vmax/KM)[S], corresponds to Km >> [S], in other words Vmax/KM is the first order rate constant found when the substrate concentration approaches zero ... [Pg.345]

Another possibility is that the denaturation of different forms of the enzyme proceeds with different rate constants (Greulich and Ludwig, 1977). As a simple example, let us consider the two forms free enzyme E and the substrate complex ES. Now, the denaturation rate of the total enzyme concentration [E]to, = [E] + [ES] is... [Pg.161]

Plots devised by Dixon to determine K, for tight-binding inhibitors, (a) A primary plot of v versus total inhibitor present ([/Id yields a concave line. In this example, [S] = 3 x Km and thus v = 67% of Straight lines drawn from Vo (when [/It = 0) through points corresponding to Vq/2, Vq/3, etc. intersect with the x-axis at points separated by a distance /Cj app/ when inhibition is competitive. When inhibition is noncompetitive, intersection points are separated by a distance equivalent to K. The positions of lines for n = 1 and n = 0 can then be deduced and the total enzyme concentration, [EJt, can be determined from the distance between the origin and the intersection point of the n = 0 line on the x-axis. If inhibition is competitive, this experiment is repeated at several different substrate concentrations such that a value for K, app is obtained at each substrate concentration. (b) Values for app are replotted versus [S], and the y-intercept yields a value for /Cj. If inhibition is noncompetitive, this replot is not necessary (see text)... [Pg.126]

If Cj denotes the total enzyme concentration, then the fractional saturation at site A is... [Pg.259]

As an extreme example, suppose that R binds to the active site A itself. Hence, any complex formed by E and R removes some of the enzymes from our consideration in Eq. (8.2.1). The total enzyme concentration is now... [Pg.260]

The velocities of reactions (1) and (2), and V2, can be expressed in terms of the total enzyme concentration (or total heme groups) [E] and the concentration of enzyme-substrate complex [ES], as... [Pg.59]

Protein concentrations are often reported in terms of mass per unit volume (eg., mg/ml) or in units of activity per volume. Care should be exercised when using these forms of concentrations. To have valid steady-state kinetics, the total enzyme concentration must be much less than the substrate concentration. Hence, one should always be cognizant of the true concentration of active enzyme in terms of molarity. [Pg.163]

In standard kinetic studies, the initial velocity (v) should be directly proportional to the total enzyme concentration. Indeed, this plot should be one of the first items analyzed in the kinetic characterization of an enzyme. The enzyme concentration range in this plot should span from below to above the concentration to be used in the inital rate studies (and, ideally, the line should go through the origin). When curvature is observed in such plots, there are several potential explanations . ... [Pg.241]

An enzyme is said to obey Michaelis-Menten kinetics, if a plot of the initial reaction rate (in which the substrate concentration is in great excess over the total enzyme concentration) versus substrate concentration(s) produces a hyperbolic curve. There should be no cooperativity apparent in the rate-saturation process, and the initial rate behavior should comply with the Michaelis-Menten equation, v = Emax[A]/(7 a + [A]), where v is the initial velocity, [A] is the initial substrate concentration, Umax is the maximum velocity, and is the dissociation constant for the substrate. A, binding to the free enzyme. The original formulation of the Michaelis-Menten treatment assumed a rapid pre-equilibrium of E and S with the central complex EX. However, the steady-state or Briggs-Haldane derivation yields an equation that is iso-... [Pg.467]

Reactions in which the velocity (v) of the process is independent of the reactant concentration, following the rate law v = k. Thus, the rate constant k has units of M sAn example of a zero-order reaction is a Michaelis-Menten enzyme-catalyzed reaction in which the substrate concentration is much larger than the Michaelis constant. Under these conditions, if the substrate concentration is raised even further, no change in the velocity will be observed (since v = Umax)- Thus, the reaction is zero-order with respect to the substrate. However, the reaction is still first-order with respect to total enzyme concentration. When the substrate concentration is not saturating then the reaction ceases to be zero order with respect to substrate. Reactions that are zero-order in each reactant are exceedingly rare. Thus, zero-order reactions address a fundamental difference between order and molecularity. Reaction order is an empirical relationship. Hence, the term pseudo-zero order is actually redundant. All zero-order reactions cease being so when no single reactant is in excess concentration with respect to other reactants in the system. [Pg.713]

Eo] or Eo Total enzyme concentration ge Degeneracy of the lower state... [Pg.801]

B) Synergistic effect on the hydrolysis of Avicel by CBH I/CBH II (pH 5.0, 37°C). CBH I and CBH II in different combinations (abscis) are mixed with Avicel (30 mg/ml). The total enzyme concentration is always 10 /iM and reducing sugars in the supernatant measured after 45 min incubation. [Pg.583]


See other pages where Total enzyme concentration is mentioned: [Pg.1082]    [Pg.437]    [Pg.115]    [Pg.137]    [Pg.100]    [Pg.113]    [Pg.179]    [Pg.191]    [Pg.220]    [Pg.251]    [Pg.643]    [Pg.132]    [Pg.252]    [Pg.102]    [Pg.248]    [Pg.275]    [Pg.466]    [Pg.509]    [Pg.678]   
See also in sourсe #XX -- [ Pg.398 ]

See also in sourсe #XX -- [ Pg.354 ]




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