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. But now we know that some enzymes are actually RNA molecules. So RNA molecules, certain RNA molecules also have the ability to catalyze reactions as we'll see eventually. And the last thing we're going to mention about enzymes is enzymes are not actually used up or not depleted in chemical reactions.