Binding inhibition

Fig. 6. Determination of the amount of free DAS required to cause 50% binding inhibition, ID q, of aDAS—AP to immobilized DAS, as a means to...

Slow, tight-binding inhibition occurs when slow-binding inhibition takes place at inhibitor concentrations comparable to that of the enzyme, in which case the previous two mechanisms can still apply. Comprehensive review articles on the subject of tight, slow, and slow, tight-binding inhibitors ate available in the literature (12,14). 

Troponin C Troponin I Troponin T Minor M protein 18 21 31 165 2 M line Ca binding Inhibits actin-myosin interaction Binds to tropomyosin Binds to myosin... 

Palese P, Tobita K, Ueda M, Compans RW (1974b) Characterization of temperature sensitive influenza virus mutants defective in neuraminidase. Virology 61 397 10 Pegg MS, von Itzstein M (1994) Slow-binding inhibition of sialidase from influenza virus, Biochem Mol Biol Int 32 851-858... 

This early biological result spurred a variety of biochemical studies of the interactions of various polyamides with the basal transcription machinery and TE-DNA complexes. Two studies have used promoter scanning to identify sites where polyamide binding inhibits transcription [64, 65]. The method uses a series of DNA constructs with designed polyamide binding sites at varying distances from... 

If the inhibition is found to be rapidly reversible, we must next determine if the approach to equilibrium for the enzyme-inhibitor complex is also rapid. As described in Chapter 4, some inhibitors bind slowly to their target enzymes, on a time scale that is long in comparision to the time scale of the reaction velocity measurement. The effect of such slow binding inhibition is to convert the linear progress curve seen in the absence of inhibitor to a curvilinear function (Figure 5.10). When nonlinear progress curves are observed in the presence of inhibitor, the analysis of... 

The hallmark of slow binding inhibition is that the degree of inhibition at a fixed concentration of compound will vary over time, as equilibrium is slowly established between the free and enzyme-bound forms of the compound. Often the establishment of enzyme-inhibitor equilibrium is manifested over the time course of the enzyme activity assay, and this leads to a curvature of the reaction progress curve over a time scale where the uninhibited reaction progress curve is linear. We saw... 

In this section we focus on differentiating slow binding inhibition due to the mechanisms shown in schemes B and C of Figure 6.3. 

On the other hand, when K Kf, the concentration of inhibitor required to observe slow binding inhibition would be much less than the value of K, for the inhibitor encounter complex. When, for example, the inhibitor concentration is limited, due to solubility or other factors, and therefore cannot be titrated above the value of Kif the steady state concentration of the El encounter complex will be kinet-ically insignificant. Under these conditions it can be shown (see Copeland, 2000) that Equation (6.6) reduces to... 

In this chapter we consider the situation where this assumption is no longer valid, because the affinity of the inhibitor for its target enzyme is so great that the value of K w approaches the total concentration of enzyme ( / T) in the assay system. This situation is referred to as tight binding inhibition, and it presents some unique challenges for quantitative assessment of inhibitor potency and for correct assessment of inhibitor SAR. 

Effects of Tight Binding Inhibition on Concentration-Response Data 179... 

EFFECTS OF TIGHT BINDING INHIBITION ON CONCENTRATION-RESPONSE DATA... 

The main issue with tight binding inhibition, from a medicinal chemistry perspective, is the limitations imposed by this behavior on following SAR. As the inhibitor affinity increases to the point where Arfpp is less than or equal to the enzyme con-... 

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