I want to know the difference in the way these compounds binding site with urease.
Is Acetohydroxamic acid a competitive or noncompetitive inhibitor.
Irrespective of the enzyme, a competitive inhibitor is analogous to the substrate and binds at the substrate binding site, thereby preventing the binding of the substrate which ensues in absence of any reaction and thus enzyme inhibition. It can be reversed by increasing the concentration of the substrate.
Acetohydroxamic acid is a competitive inhibitor of urease.
A noncompetitive inhibitor binds near or remote to the substrate binding site. This is also reversible, however, not by increasing the concentration of the substrate.
Hydroxylamine is a noncompetitive inhibitor of urease.
But I see this paper said it is noncompetitive
http://www.jbc.org/content/240/6/2407.long
Hi there,
In the summary acetohydroxamic acid is described as a potent irreversible inhibitor therefore you can't describe it strictly as a competitive or non competitive inhibitor (these being reversible inhibitors)...
Competitive inhibitors usually bind in the active site, but this is not necessary. The operational definition is that a competitive inhibitor elevates the Km of the substrate but does not change Vmax.
Inhibitors can be reversible or irreversible, but the use of steady-state kinetics theory to describe the behavior of inhibitors is usually limited to those reversible inhibitors that are in rapid equilibrium with the enzyme. This is not the case with irreversible inhibitors, or reversible inhibitors with slow-binding kinetics or long residence time.
Therefore, attempting to use steady-state kinetics equations to distinguish between competitive and non-competitive inhibitors that are irreversible, or reversible with slow-on or slow-off kinetics, can lead to confusion.
To find out whether steady-state kinetics are appropriate to the analysis of an inhibitor, one should look at the reaction progress curves (i.e. product versus time) with various inhibitor concentrations, starting the reactions by adding enzyme (do not pre-incubate the enzyme with the inhibitor). If the progress curves are all linear (during the period of time during which the progress curve for the uninhibited reaction is linear), then the inhibitor is in rapid equilibrium and steady-state kinetics are appropriate. If the curves with inhibitor slow down with time, then you have non-steady-state situation requiring a different analysis suitable for time-dependent inhibition.
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