Effect of substrate concentration

In order to investigate the effect of the substrates molar ratio on the reaction performance, the concentrations of the enzyme and antioxidant were kept constant, whereas that of the acyl donor was increased. In the case of rutin, independently of the molar ratio, used the acylation proceeded with low yields, while only monoesters were formed in all reaction systems used. The same behavior was observed in the case of silybin using tert-amyl alcohol and tert-butyl alcohol as reaction media (data not shown). In contrast, when acetone was used as medium the conversion yield for the acylation of silybin increased as the molar ratio was increased (Table 9.2). 

Molar ratio Conversion % (initial reaction rates in mmol/h/g of biocatalyst)  

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The effect of substrate concentration on specific growth rate (/i) in a batch culture is related to the time and p,max the relation is known as the Monod rate equation. The cell density (pcell) increases linearly in the exponential phase. When substrate (S) is depleted, the specific growth rate (/a) decreases. The Monod equation is described in the following equation ... 

Figure 8-3. Effect of substrate concentration on the initial velocity of an enzyme-catalyzed reaction.

THE MICHAELIS-MENTEN HILL EQUATIONS MODEL THE EFFECTS OF SUBSTRATE CONCENTRATION... 

Effect of substrate concentration on PG inhibitor Polygalacturonase activity was measured, with or without inhibitor, at different concentrations of the substrate in the reaction mixture to understand the mode of inhibition of polygalacturonase by D. maculata stem inhibitor. The data presented in Fig. 1 indicate that the nature of inhibition is mixed-type. The inhibitor affects both Km as well as Vmax of polygalacturonase. 

Allard A-S, M Remberger, AH Neilson (1985) Bacterial O-methylation of chloroguaiacols effect of substrate concentration, cell density and growth conditions. Appl Environ Microbiol 49 279-288. 

The effect of substrate concentration and the important issue of the existence or otherwise of threshold concentrations below which degradation is not effectively accomplished. 

Extensive studies on the effect of substrate concentration and on the bioavailability of the substrate to the appropriate microorganisms have employed samples of natural lake water supplemented with suitable nutrients. There are few additional details that need to be added since the experimental methods are straightforward and present no particular difficulties. Considerable use has also been made of a comparable methodology to determine the fate of agrochemicals in the terrestrial environment. 

Table 5.1 Characteristic effects of substrate concentration on the IC50 value for reversible enzyme inhibitors of different modalities...

The inhibition modality for a slow binding inhibitor is easily determined from the effects of substrate concentration on the value of k0bs at any fixed inhibitor concentration (Tian and Tsou, 1982 Copeland, 2000). For a competitive inhibitor the value of fcobs will diminish hyperbolically with increasing substrate concentration according to Equation (6.15) ... 

Examples of the expected effect of substrate concentration on the value of kt)bs for these three inhibition modalities are illustrated in Figure 6.9. 

Figure 6.9 Effect of substrate concentration (relative to KM) on the value of kAs at a fixed concentration of a slow binding inhibitor that is competitive (closed circles), uncompetitive (open circles), or noncompetitive (a = 1, closed squares) with respect to the varied substrate.

Figure 6.22 Effect of substrate concentration on the value of A j, for inhibition of COX2 by 30 rM DuP697.

Since the effects of substrate concentration on the velocity of a cooperative enzyme are not described by a hyperbola (Michaelis-Menten), it s not really appropriate to speak of Km s. The term reserved for the special concentration of substrate that produces a velocity that is one-half of... 

This relation is the broadly known Michaelis-Menten equation. The effect of substrate concentration ni on the rate predicted by this equation follows a characteristic pattern. Where substrate concentration is considerably smaller than the half saturation constant (ni <reactive intermediate EA depends on the availability of the substrate A. In this case, (mA + K A ) and reaction rate r+ given by 17.18 is proportional to mA. For the opposite case, (mA K ), little free enzyme E is available to complex with A. Now, (mA + mA and reaction... 

Effect of substrate concentration. In the following experiments the cholinesterase activities were measured by a continuous titration method. The digest of acetylcholine and horse-serum cholinesterase (total vol. 10 ml.), containing bromothymol blue and 0-0002 m phosphate, was titrated with 0-01 n NaOH to maintain the pH at 7-4. The titrations, which were carried out at 20°, were linear over a period of 10-15 min. The velocity was expressed as ml. 0-01 n NaOH/5 min. under the conditions used, it was proportional to the enzyme concentration. When an inhibitor was added, this was equilibrated with the enzyme, etc., for 5 min. at 20° before adding the substrate contained in a volume of 1 ml. 

Fig. 13. Effect of substrate concentration on inhibition of horse-serum cholinesterase.1 Enzyme activity was estimated by titration with 0-01 n NaOH at pH 7-4 and 20°. — , control, no inhibitor x — x, 2x 10 7 m eserine 0—O, 5 x 10 8 m di-isopropyl phosphorofluoridate.

Experimental studies on the effect of substrate concentration on the activity of an enzyme show consistent results. At low concentrations of substrate the rate of reaction increases as the concentration increases. At higher concentrations the rate begins to level out and eventually becomes almost constant, regardless of any further increase in substrate concentration. The choice of substrate concentration is an important consideration in the design of enzyme assays and an understanding of the kinetics of enzyme-catalysed reactions is needed in order to develop valid methods. 

Figure 8.3 The effect of substrate concentration on the activity of an enzyme. At...

Some experiments were performed to observe the effect of substrate concentration in input flow on the bioreactor temperature behavior. All experiments were run, at least, along one week. The main idea behind these runs was to analyze (a) the effect of reference and inlet concentration and (b) the effect of the parameters of the controller (6). Thus, the following results were chosen for discussing the oscillatory behavior of the bioreactor temperature ... 

Wang, Y.-S., Subba-Rao, R.V., and Alexander, M. Effect of substrate concentration and organic and inorganic compounds on the occurrence and rate of mineralization and cometabolism, Appl. Environ. Microbiol, 47(6) 1195-1200, 1984. 

FIGURE 6-11 Effect of substrate concentration on the initial velocity of an enzyme-catalyzed reaction. V max is extrapolated from the plot, because V0 approaches but never quite reaches /max. The substrate concentration at which V0 is half maximal is Km, the Michaelis constant. The concentration of enzyme in an experiment such as this is generally so low that [S] >> [E] even when [S] is described as low or relatively low. The units shown are typical for enzyme-catalyzed reactions and are given only to help illustrate the meaning of V0 and [S]. (Note that the curve describes part of a rectangular hyperbola, with one asymptote at /max. If the curve were continued below [S] = 0, it would approach a vertical asymptote at [S] = — Km.)... 

Effect of substrate concentration on reaction velocities for two enzymes enzyme 1 with a small Km, and enzyme 2 with a large Km. 

Kinetic analysis is one of the most basic topics of en-zymology. Such studies reveal not only how fast an enzyme can function, but also its preferences for various reactants (or substrates as they usually are called), the effect of substrate concentration on the reaction rate, and the sensitivity... 

Substrate Concentration One of the most widely employed expressions for the effect of substrate concentration on jj. is the Monod equation, which is an empirical expression based on the form of equation normally associated with enzyme kinetics or gas adsorption 1... 

Beyenal, H., and Z. Lewandowski. 2000. Combined effect of substrate concentration and flow velocity on effective diffusivity in biofilms. Water Research 34 528-538. 

Reinke, L.A. et al., Conjugation of p-nitrophcnol in the perfused rat river The effect of substrate concentration and carbohydrate reserves, J. Pharmacol. Exp. Then, 217, 863, 1981. 

Figure 2. The effect of substrate concentration on hydrogen yield. Other variables are constant at their respective levels as follows initial pH = 7 1.0% HC1 pretreated substrate...

Figure 6 (a) Effect of substrate concentration on product formation. , 0.063 mg/ml ... 

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