Salivary amylase is an enzyme that breaks starch down into sugar and is present in human saliva, where it begins the chemical process of digestion. The primary function of the bile salt is the emulsification of fats. Emulsification is the process, where large globules of fat are broken down into smaller globules. Rennin also called chymosin is the protein digesting enzyme that curdles milk by transforming caseinogen into insoluble casein. It is synthesized by chief cells in the stomach. Pepsin is an enzyme released by the chief cells in the stomach and that degrades food proteins into peptides. Steapsin is a digestive enzyme of pancreatic juice that catalyzes the hydrolysis of fats to fatty acids and glycerol.