Figure 3.

Active site of papain (1KHP⁴⁴) (left), caspase-3 (1PAU⁴⁵) (middle), and human legumain (4AW9³⁷) (right). The active site residues are represented as sticks; the enzyme carbons are colored gray. The substrate carbons are colored orange, and the relevant crystal structure waters are depicted as red spheres. Dotted lines denote hydrogen bonds.