Non-Competitive Inhibitor & Active Site

[blazinfury]

A non-competitive inhibitor tends to bind at an allosteric site and prevents enzyme function. However, can the substrate still bind the enzyme even though there will be no activity as long as non-competitive inhibitor is bound? Or does the active site change conformation as well, thus preventing the substrate from binding?

Edited February 23, 2013 by blazinfury

[CharonY]

Both can happen. The allosteric inhibitor generally causes a conformational change in the enzyme which in some cases leads to a reduction in substrate affinity but can also just lower the enzymatic activity (based on the extent and type of conformational change).

[BabcockHall]

Noncompetitive inhibition is sometimes seen when an enzyme binds two substrates and the inhibitor resembles the substrate that is not varied. For example adenosine diphosphoribose (which resembles a portion of NAD) is a noncompetitive inhibitor versus formate with respect to the enzyme formate dehydrogenase. Some books refer to noncompetitive inhibition as mixed inhibition, potentially leading to confusion. Noncompetitive inhibitors bind in the presence or the absence of substrates.