And it basically carries out a set of two closely related reactions. In one of the reactions, it basically cleaves peptide bonds on the carboxyl side of lysine. In the other reaction, it binds and cleaves. On the carboxyl side of the arginine amino acid so this trypsin has a single type of has a single type of substrate, namely the polypeptide and it carries out two sets, two types of very similar reactions in one reaction and Cleaves lysine on the carboxyl side in the other reaction cleaves Arginine on the carboxyl side. Now, number five nearly all enzymes are proteins. So long ago we essentially thought that all enzymes were proteins.