What is the protein portion of an enzyme called?

Which one of the following statements is true regarding enzymes?

Assertion : Enzymes lower the activation energy.
Reason : $A$ substrate molecule can be acted upon by a particular enzyme.

Proteins that possess catalytic activity are called . . . . . . .

The enzyme invertase catalyzes the hydrolysis of .......

An enzyme obtained from an animal source has been classified by the Enzyme Commission and allocated its unique four-digit number $1.2.1.4$. To which of the following classes does it belong?