Which feature distinguishes enzymes from other proteins?

Enzymes are a unique subset of proteins that possess certain distinguishing features which enhance their functionality in biochemical reactions. One of the most significant characteristics is their ability to undergo conformational changes. This property allows enzymes to adapt their structure to better fit substrates during the catalysis process, thereby facilitating the formation of the enzyme-substrate complex.

Another key feature of enzymes is their specificity for substrates. Enzymes are designed to recognize and bind to specific molecules, which ensures key biochemical reactions occur with accuracy and efficiency. This specificity is often attributed to the precise structure of the active site, the region of the enzyme where the substrate binds.

Additionally, the presence of active sites is essential to the function of enzymes. The active site is uniquely shaped to accommodate the enzyme's specific substrate, contributing to the enzyme's ability to lower the activation energy of the reactions they catalyze.

Considering these points, all these features—conformational changes, substrate specificity, and the presence of active sites—collectively characterize enzymes and set them apart from other types of proteins. This multifaceted approach is why the correct answer encompasses all of the features mentioned.