A protease is a member of a very large group of enzymes that have a variety of functions in the body. A primary one is as a digestive enzyme to process protein. This process is called proteolysis, and it turns protein molecules into shorter fragments, called peptides, and eventually into their components, called amino acids. Other types of proteases are involved in the regulation of cellular events, such as blood clotting. These are also called proteolytic enzymes or proteinases.