What is the catalysis mechanism used by proteases?

Proteases catalyze the breakdown of peptide bonds within proteins through one of the two mechanisms:

• By activating a water molecule which then performs a nucleophilic attach on the peptide bond to hydrolyze it. Proteases using this mechanism are aspartic, glutamic and metallo- proteases.
• By utilizing a nucleophilic residue within a catalytic triad to perform a nucleophilic attack, covalently linking the protease to the substrate protein and releasing the first half of the product. The activated water then attacks this intermediate and complete the catalysis process, releasing the second half of the product and regenerating the free enzyme. Examples of proteases exploiting this mechanism are Serine, threonine and cysteine proteases.