Defining "Inhibiting" and "Allosterically Regulating"

[asdf1122]

Can anyone please explain the difference between "Inhibiting" a protein and "Allosterically regulating" a protein?

 

Thanks in advance.

[MedGen]

IIRC allosterically is an indirect method of regulation, e.g. tyrosine/serine/threonine phosphorylation as seen in most signalling pathways that require the activation or inactivation of a protein, that requires the modification of the target protein.

 

Inhibition mostly relates to the direct competitive inhibitors that compete with an enzymes substrate(s) in the active site thus preventing the enzyme from catalysing the reaction it would normally.

 

Hence allosteric inhibitors do it from behind, they don't actively compete for the active site.

[CharonY]

Almost, but not quite. Activation (or inhibition for that matter) by posttranslational modification are normally not considered to be allosteric regulation. Allosteric regulation is characterized by binding of a ligand at a specific site of the enzyme that is not the active site. Again, it does not refer to a modification of the enzyme itself.

 

Moreover, "inhibiting" refers to all means of inhibition (of which allosteric is but a subgroup) , what is meant in the OP is probably "competitive inhibition" vs. allosteric inhibition.

 

Note that allosteric regulation can be both activating as well as inhibiting. Competive modes of regulation are, per definitionem, always inhibitory.

Also I should add that the binding of the ligand to the allosteric site leads to confirmation changes resulting in activation/inactivation of the protein. Binding of a competitor blocks the active site, but does not necessarily result in larger confirmation changes.

Edited October 6, 2008 by CharonY

[MedGen]

Thanks for the correction.