ACTIVE SITES OF ENZYMES HAVE SOME COMMON FEATURES The active site of an enzyme is the region that binds the substrates(and the prosthetic group, if any) and contains the residues that directly partic. ipate in the making and breaking of bonds. These residues are called the catalytic groups. Although enzymes differ widely in structure, specificity, and mode of catalysis, a number of generalizations concerning their ac- tive sites can be stated