Question

Are enzymes tertiary proteins?

Answer 1

It would depend.

Explanation:

It would completely depend on the enzyme we're considering. Some are only monomeric (e.g. trypsin), some contain several subunits which interact to form a quaternary structure.

Proteins' tertiary structures are how amino acid sequences fold in three-dimensional space to a free-energy minimum.

In the case of trypsin, a serine protease, we could say the enzyme only has a tertiary structure. However, I would wager that there are more proteins with quaternary structures.