Anoncompetitive inhibitor decreases the rate of an enzymatic reaction by

The answer is Binding itself to the allosteric site.

Explanation:

A noncompetitive inhibitor decreases the rate of an enzymatic reaction by binding itself to the allosteric site. This means that the inhibitor isn't placed in the active site, but it binds to another place, called the allosteric site. This changes the enzyme conformation causing the enzyme activity to be reduced.