So let's begin by discussing the role that each one of these amino acids actually plays in promoting the hydrolysis of peptide bonds. Well, let's begin with serine 195. We know that Kyotrypsin is an example of a Serene protease. And so what that means is it's ultimately the serine residue inside the active side. It's this residue here that acts as a nucleophile and will attack the carbon of the carbonyl that peptide bond nucleophilically. And we'll see exactly how that works out in just a moment.