Active sites of serine protease contain
Serine proteases name stems from the nucleophilic Ser (serine) in the enzyme active site Nucleophilicity of the catalytic Ser is typically dependent on a catalytic triad of Asp, His, and Ser residues, commonly referred to as the charge relay system Ref: biochemistry by U. Satyanarayana 3rd edition Pgno : 171
Histidine
Lysine or threonine
Arginine
Serine
Structure and function of protein