1. Serine Proteases A large group of enzymes that cleave amide bond
Trpsin, Chymotrypsin and Elastase in protein degradation
All made in Pancreas and function in intestine (digestion of proteins)
Same reactivity and mechanism but different selectivity
Trypsin cleaves after Lys and Arg
Chymotrypsin after bulky hydrophobic residue
Related structuraly 240 amino acids with ~40% homolgy. They all have 3 amino (Asp, His and Ser) residues conserved

4. Two additional H-bonds in transition state
Enzyme binds transition state stronger than it does starting material or the products.

5. Proteins formed in an inactive form (proenzymes)
In case of trypsin, enteropeptidase (serine protease) cleaves trypsinogen N terminus after Lys 15.
That allows the formation of the active conformation.
Protease inhibitors.