So we discussed chimera, Trypton, trypsin and elastics. Now, we said these three serum proteases all use the same catalytic triad. So in their active side, they have this collection of three amino acids that work together to basically promote the hydrolysis of peptides side bonds. And out of these three amino acids, it's the serine that acts as the nucleophilic agent. Now, what about the other categories of proteases? So remember, we not only have seren proteases, but we also have cysteine proteases aspertal proteases metalloprotiases.