Final answer:
The active site of carboxypeptidase is formed by the three-dimensional arrangement of specific amino acid residues, a small portion of the enzyme, achieved through the protein's folding into its tertiary structure.
Step-by-step explanation:
The active site of an enzyme, such as carboxypeptidase, is formed by the unique three-dimensional arrangement of amino acids that are not necessarily contiguous along the primary sequence of the protein. Instead, amino acids that are often widely separated in the primary sequence are brought together by the folding of the protein into its tertiary structure, creating a specific environment suitable for catalysis.
Experimental data shows that the active site is usually a tiny portion of the enzyme, about 10% to 20%. This site often includes amino acids like His, Cys, Asp, Arg, and Glu due to their functional groups capable of hydrogen bonding and acid-base catalysis. These amino acid residues are crucial for the enzyme's activity, sometimes involving a mere handful out of hundreds that make up the enzyme, as illustrated by the structure of other enzymes like human carbonic anhydrase.
Additionally, carboxypeptidase is an exopeptidase that cleaves amino acids from the carboxy-terminal end, and like many other enzymes, it can require a prosthetic group such as a metal ion, or not, depending on the specific type of carboxypeptidase.