In experimental tests of enzyme evolution, a gene encoding an enzyme was subjected to multiple cycles of random mutagenesis and selection for altered substrate specificity. The resulting enzyme had altered substrate specificity and multiple amino acid changes. Where in the enzyme would you expect these amino acid changes to be located?
A) only in or near the active site
B) only in the hydrophobic interior of the folded protein
C) only at surface sites distant from the active site
D) in or near the active site and at surface sites distant from the active site

Question

Quizplus · Accepted Answer

The alterations in substrate specificity and multiple amino acid changes suggest that mutations have occurred in or near the active site, which is responsible for the enzyme's catalytic activity. However, since the mutated enzyme was still functional and able to perform its job, it is likely that mutations have also occurred at surface sites that were distant from the active site. These changes may have altered the enzyme's overall structure and stability, allowing it to accommodate different substrates while maintaining its catalytic activity. Therefore, both the active site and surface sites distant from the active site could be affected by the evolution of new enzyme functions.

In Experimental Tests of Enzyme Evolution, a Gene Encoding an Enzyme