Inhibitors kinetics

Microsomes are widely used to study the metabolism of xenobiotics. Enzymes can be chararacterized on the basis of their requirement for cofactors (e.g., NADPH, UDPGA), and their response to inhibitors. Kinetic studies can be carried out, and kinetic constants determined. They are very useful in studies of comparative metabolism, where many species not available for in vivo experiment can be compared with widely investigated laboratory species such as rats, mice, feral pigeon, Japanese quail, and rainbow trout. 

Larsson, O. M., Falch, E., Schousboe, A., and Krogsgaard-Larsen, P. (1991) GABA uptake inhibitors Kinetics and molecular pharmacology, in Presynaptic Receptors, and Neuronal Transporters (Langer, S. Z., Galzin, A. M., and Costentin, J., eds.), Pergamon Press, Oxford, UK, pp. 197-200. 

Abstract Neuroscientists may wish to quantify an enzyme activity for one of many reasons. In order to do so, the researcher must be able to set up an assay appropriately, and this requires some understanding of the kinetic behavior of the enzyme toward the substrate used. Furthermore, such an understanding is vital if the inhibitory effects of a drug are to be assessed appropriately. This chapter outlines key principles that must be adhered to, and describes basic approaches by which rather complex kinetic data might be obtained, in order that enzyme kinetics and inhibitor kinetics might be studied successfully by the nonexpert. 

Selected entries from Methods in Enzymology [vol, page(s)] Add-base catalysis [with site-directed mutants, 249, 110-118 altered pH dependencies, 249, 110] commitment to [in determination of intrinsic isotope effects, 249, 343, 347-349 in interfacial catalysis, 249, 598-599 equilibrium isotope exchange in, 249, 443-479 hydrogen tunneling in, 249, 373-397] interfacial [competitive inhibitors, kinetic characterization, 249, 604-605 equilibrium parameters, 249, 587-594 forward commitment to, 249, 598-599 interpretation, 249, 578-586 (constraining variables for high processivity, 249, 582-586 kinetic variables at interface,... 

THROMBOXANE A SYNTHASE THYMIDINE 2 -HYDROXYLASE THYMIDYLATE SYNTHASE TIGHT-BINDING INHIBITOR KINETICS HENDERSON PLOT Tight-binding inhibitors,... 

HENDERSON PLOT TIGHT-BINDING INHIBITOR KINETICS TIGHT ION PAIR LOOSE ION PAIR ION PAIR... 

Figure 1 Graphical depiction of Lineweaver-Burk expression for determination of competitive inhibitor kinetic constants. 2 WiLEY ENCYCLOPEDiA OF CHEMiCAL BiOLOGY 2008, John Wiiey Sons, inc.

Figure 5 Lineweaver-Burk plots for determination of uncompetitive inhibitor kinetic constants, by Equation 6.

The aldol reaction of a silyl enol ether proceeds in a double and two-directional fashion, upon addition of an excess amount of an aldehyde, to give the silyl enol ether in 77 % isolated yield and more than 99 % ee and 99 % de (Sch. 33) [92]. This asymmetric catalytic aldol reaction is characterized by kinetic amplification of product chirality on going from the one-directional aldol intermediate to the two-directional product. Further transformation of the pseudo C2 symmetric product still protected as the silyl enol ether leads to a potent analog of an HIV protease inhibitor. Kinetic resolution of racemic silyl enol ethers by the BINOL-Ti catalyst (1) has been reported by French chemists [93]. 

Inhibitor kinetics The IC50 determinations described herein provide a simple method of comparing protease inhibitors. However, it may be desirable to characterize the interactions of inhibitors with the enzyme in more detail. Both the chromogenic and fluorescence assays can be read in kinetics mode on the machines described to give real-time rate measurements for use in determining kinetic parameters. 

Key words TNAP, PHOSPHOl, Vascular smooth muscle cells. High-throughput screening. Small-molecules, Pharmacological inhibitors. Kinetic studies. Cell culture... 

Enzyme kinetics is the quantitative study of enzyme catalysis. Kinetic studies measure reaction rates and the affinity of enzymes for substrates and inhibitors. Kinetics also provides insight into reaction mechanisms. 

Excitable media are some of the most commonly observed reaction-diffusion systems in nature. An excitable system possesses a stable fixed point which responds to perturbations in a charaeteristie way small perturbations return quiekly to the fixed point, while larger perturbations that exceed a certain threshold value make a long excursion in concentration phase space before the system returns to the stable state. In many physical systems this behaviour is captmed by the dynamics of two concentration fields, a fast aetivator variable u with cubic nullcline and a slow inhibitor variable u with linear nullcline [33]. The FitzHugh-Nagumo equation [34], derived as a simple model for nerve impulse propagation but which can also apply to a chemical reaction scheme [35], is one of the best known equations with sueh activator-inhibitor kinetics ... 

A novel teehnique has been developed for determining the concentration of hydrate inhibitors in the aqueous phase and monitoring the hydrate safety margin. By measuring the electrical conductivity and acoustic velocity, the developed C-V prototype device can determine the concentrations of thermodynamic hydrate inhibitors, kinetic hydrate inhibitors, and salts. Integrating with a thermodynamic model, it ean also determine the hydrate stabihty zone hence the hydrate safety margin if the hydrocarbon composition and the operating conditions are known. Intensive evaluation was conducted under both lab and field conditions. The results demonstrate that the C-... 

Keywords Corrosion Inhibitor, Kinetic Hydrate Inhibitor, HPLC, Iodine Complexation, Size Exclusion Chromatography. 

We start from a general reaction-diffusion system with activator-inhibitor kinetics in one spatial dimension with coordinate r. 

In contrast to the instabihty of uniform oscillations, the physical origin of the wavefront instability seems to have some relation to the conventional diffusion instability. To see this, we first give a brief quaUtative interpretation of the conventional diffusion instabihty. Here the notions activator and inhibitor seem to be helpful, and for simpUcity we imagine a two-component activator-inhibitor system. The instability then turns out to be due to relatively rapid diffusion of the inhibiting substance. Consider the activator-inhibitor kinetics (first, without diffusion) ... 

Sequential biocatalytic cascade reactions are characterized by the use of multiple enzymatic steps involving various biocatalysts. One cascade reaction can consist of an enzyme-module with several enzymes if substrate and inhibitor kinetics are compatible with these combinations. Sequential use of such enzyme-modules surpassing the work-up of intermediate products is the criterion for the idea of cascade reactions we address here on the one hand, the synthesis of nucleotide sugars and their derivatives, on the other hand, the synthesis of glycan epitopes with multiple GTs. 

The challenge in analyzing a metabolic network is the determination of the flux control coefficients. ft is possible to determine them directly by enzyme titration combined with the measurement of the new steady-state flux. For in vivo systems this would require alteration of enzyme expression through an inducible promoter and is not very practical for a moderately sized network. A more common method of altering enzyme activities involves titration with a specific inhibitor. However, this technique can be compHcated by nonspecific effects of the added inhibitor and unknown inhibitor kinetics. 

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