In fact, these enzymes contain two so a pair of aspartic acids. And as we'll discuss in a future lecture, one of those residues takes away an H atom and the other residue basically is used to increase the nucleophilic character of that particular substrate molecule. And Renan or Renin is basically an example of an aspartal protease that is involved in increasing or decreasing so regulating the blood pressure inside our body. And we also have another example, namely Pepsin. And Pepsin is once again an example of a digestive enzyme. It's used to break down the proteins that we ingest into our body.