The allosteric enzymes on the top of active sites contain

The correct option is "allosteric site".

Explanation:

Enzymes are biological catalysts that speed up chemical reactions in living organisms. Most enzymes possess a primary binding region known as the active site, where the specific substrate binds to undergo a chemical reaction.

However, allosteric enzymes are a unique class of regulated enzymes. In addition to their active sites, they possess distinct regulatory regions located elsewhere on the enzyme structure, typically on the top or away from the active sites. These specialized regulatory regions are called allosteric sites.

When specific effector molecules (which can be activators or inhibitors) bind to the allosteric site, they induce a conformational (shape) change in the enzyme. This structural modification alters the shape of the active site, thereby regulating the enzyme's catalytic activity (either enhancing or inhibiting its ability to bind substrates).

Therefore, the specific sites that allosteric enzymes contain (distinct from/on top of their active sites) are indeed allosteric sites.