Replacing one amino acid inside a digestive enzyme's active site eliminates catalytic activity although the rest of the polypeptide appears normally folded. Which explanation best accounts for this outcome?

Core Concept

An enzyme active site depends on the three-dimensional placement and chemistry of particular amino acid side chains. Replacing a residue that directly participates in substrate binding or catalysis can eliminate activity even if the rest of the protein remains folded. The effect depends on the role and location of the substituted residue, so not every active-site substitution has the same consequence.