Question

Enzymes with two sites are called
(A) Apoenzyme
(B) Holoenzyme
(C) Allosteric enzyme
(D) Conjugate enzyme

Answer 1

Hint: Enzymes are proteins which are used to catalyse the biological reaction by increasing the rate of reaction without being indulged itself at the end of the reaction. Mostly all the enzymes consist of two active sites. These enzymes with two active sites are differentiated on the bases of enzyme requirements to be activated or need not be activated. Enzymes are proteins composed of amino groups bonded with polypeptide chains.

Complete Step by Step Answer:
Simple enzymes are those enzymes that are completely composed of protein chains (activated to attack substrate) and complex proteins are those which got activated first with the attack non-protein (cofactor) compound on the protein part of the enzyme.

Now in the complex enzyme, protein part of the enzyme is known as Apoenzyme which gets activated by the attack of the cofactor (non-protein part) resulting in the formation of an activated enzyme known as Holoenzyme or complex enzyme or conjugate enzyme. After this, it can attack the substrate to catalyse its reaction.

The site that gets activated in complex enzymes and the site which is already activated for the attack of the substrate is only one active site and these enzymes also consist of another site known as the allosteric site. This site enhances or decreases the activity of the activated enzyme (Apoenzyme in case of complex enzyme) by the attack of competitive or non-competitive inhibitors. The enzyme with two activated sites is known as the Allosteric enzyme.
Thus, the correct option is C.

Note: When a competitive inhibitor binds with an allosteric site then it molds the shape of the active site as such that substrate will not get fit in that active site or can say active site will not allow the binding of substrate. Whereas when non-competitive inhabitor bind on allosteric site then it does not affect the shape of active site and substrate can easily bind on active site.