Subtilisin and chymotrypsin both have the same catalytic triad, and a similar tertiary protein structure. This is likely due to a common evolutionary origin, conserving the residues essential for protein function. In order to allow different proteins to be targeted by the proteases, variation in the specificity pocket is used.
Faults in the specificity pockets, as well as in the catalytic triad, can cause certain cancers. These are typically caused by too much or insufficient protein cleavage.