What is Ki in competitive inhibition?
Ki, the inhibitor constant The inhibitor constant, Ki, is an indication of how potent an inhibitor is; it is the concentration required to produce half maximum inhibition. Plotting 1/v against concentration of inhibitor at each concentration of substrate (the Dixon plot) gives a family of intersecting lines.
How do you calculate Ki from slope?
Thus, KI can be determined by plotting the slope values vs. [I]. The resulting secondary plot or “replot” will have a Y-axis intercept of KM/Vmax and a slope of KM/VmaxKI. The value of KI is the slope/intercept of this replot.
Is Ki the same as KM?
Ki is a thermodynamic parameter, reporting the true affinity an inhibitor has for binding an enzyme. In contrast, Km is a kinetic parameter, which gives the substrate concentration at which half of the maximum enzymatic reaction rate is attained.
What is the Ki for an enzyme inhibitor is equivalent to?
Km
Ki for an inhibitor is analogous to Km for a substrate; a small Ki value reflects tight binding of an inhibitor to an enzyme, whereas a larger Ki value reflects weaker binding.
How can I get Ki from IC50?
Hence, IC50 = E/2 + Ki. Therefore, IC50 is dependent on the enzyme concentration, and is always larger than Ki.
What is Ki and KM?
Answer. The value Ki is the dissociation constant describing the binding affinity between the inhibitor and the enzyme, while Km is the Michaelis constant in the Michaelis-Menten equation which is used to describe the kinetics of substrate/enzyme binding.
What is the unit of KI?
Potency
| Value | Units | |
|---|---|---|
| DOSE | 5 and 10 | mg/kg |
| EC50 | 0.42 | nM(Ki) |
| Human | ||
| EC50 | 8.0 | nM |
How do you calculate Ki from Dixon plot?
Experimental Determination of Ki Using the Dixon Plot 1/v = (K + [S])/V[S] + [I](K/Ki + [S]/Ki’)/V[S], which means that at any fixed value of [S], 1/v is linearly related to the value of [I]. (A plot of 1/v vs. [I] is called a Dixon plot.)
Is Ki the same as Kd?
The difference between Kd and Ki is that Kd is a more general, all-encompassing term, whilst Ki is more narrowly used to indicate the dissociation equilibrium constant of the enzyme-inhibitor complex.
How do you interpret Ki values?
3 Therefore, the smaller the Ki, the smaller amount of medication needed in order to inhibit the activity of that enzyme. If a Ki is much larger than the maximal plasma drug concentrations a patient is exposed to from typical dosing, then that drug is not likely to inhibit the activity of that enzyme.
What does KI value mean?
The value Ki is the dissociation constant describing the binding affinity between the inhibitor and the enzyme, while IC50 is the concentration of inhibitor required to reduce the enzymatic activity to half of the uninhibited value. Both values can be used as quantitative indexes for the inhibitor potency.
How do you find KI on a graph?