Question

if pyruvate kinase requires temporary binding of mg in order to phosphorylate pyruvate, then mg must be
a heme group.
a cofactor.
none of the answers are correct
a coenzyme.
a prosthetic group.

Explanation:

Cofactors are non - protein chemical compounds or metallic ions that are required for a protein's biological activity. Since Mg is a metallic ion and is required temporarily for the activity of pyruvate kinase (to phosphorylate pyruvate), it is a cofactor. A heme group is an iron - containing prosthetic group. A coenzyme is an organic non - protein compound that binds with an enzyme to catalyze a reaction. A prosthetic group is a non - amino acid component that is tightly bound to a protein.

Answer:

a cofactor.