Question

What is obtained from the combination of apoenzyme and coenzyme?

Answer 1

Apoenzyme has to bind with a cofactor to become an active enzyme. These two combine to form the complete enzymatic entity that is functional.

Complete answer:
Apoenzymes are incomplete enzymes or protein molecules which lack the necessary non-protein components called cofactors to perform their functions.
Cofactors are the non-protein compounds that help an apoenzyme transform into its active form and assist it during the catalysis of a reaction.
These non-protein components can either be inorganic or organic compounds. Inorganic cofactors can include metal ions and organic cofactors can have molecules like heme.
Coenzymes are the small organic or metallo organic non-protein molecules that bind to an apoenzyme and help them in their enzymatic activity.
Therefore, coenzymes are a type of cofactors but their molecular weight is relatively less when compared to organic cofactors. Coenzymes usually include molecules from the vitamin B complex family.
Coenzymes are further of two divided into two categories - prosthetic groups and cosubstrates.
Prosthetic groups bind tightly to the enzyme and remain bound during the catalytic reaction. On the other hand, cosubstrates are regenerated cyclically as they pass on from one apoenzyme to the other.
When apoenzymes and cofactors combine, they form an activated and functional complex called holoenzyme.
Therefore, the inactive form of an enzyme which is present as apoenzyme gets converted into an active form called the holoenzyme after the binding of a cofactor to the complex.

Note:
Some enzymes are not functional inherently and need cofactors to make them active to perform their catalytic activity. Once that happens, their active form is known as holoenzyme.