The cofactor of the enzyme carboxypeptidase is:

The correct option is Zinc.

Step-by-step Explanation:

1. Understanding Enzymes and Cofactors:
Enzymes are biocatalysts that speed up chemical reactions in living organisms. Many enzymes require non-protein components called cofactors to become catalytically active. These cofactors can be organic molecules (like coenzymes) or inorganic metal ions.

2. Analyzing Carboxypeptidase:
Carboxypeptidase is a digestive enzyme secreted by the pancreas that plays a crucial role in the hydrolysis of peptide bonds at the carboxyl-terminal (C-terminal) end of proteins and peptides.

3. Identifying the Metal Ion Dependency:
Carboxypeptidase is a classic example of a metalloprotease. It contains a tightly bound divalent metal ion in its active site which is essential for its catalytic activity. This metal ion coordinates with the carbonyl oxygen of the peptide substrate, making it more susceptible to nucleophilic attack by water.

4. Matching with the Correct Cofactor:
The specific metal ion present as the cofactor in carboxypeptidase is Zinc (${\mathrm{Zn}}^{2+}$). Therefore, Zinc is the cofactor for carboxypeptidase.