The correct answer is: C) a cofactor necessary for enzyme activity
It has been shown that the loss of the zinc in the active side of carboxypeptidase leads to loss of enzyme activity. The enzyme can be reactivated by adding zinc, but also by adding some other divalent metals such as cobalt, or nickel.
Carboxypeptidase is an example of metaloenzyme that hydrolyzes a peptide bonds in the protein.
There are several types of carboxypeptidases in humans with diverse functions: from catabolic to protein maturation.
