Pepsin is an enzyme which degrades the food proteins into smaller units known as peptides. Pepsin is released by the chief cells in the stomach. Pepsin was discovered by Theodor Schwann in 1836. The name 'pepsin' was given to the enzyme because it was derived from the Greek word, 'peptein' which means 'to digest'. Pepsin is considered as the digestive protease and its genetic code is 8885 (HGNCid). The functions pepsin are enhanced in the acidic environments, particularly between pH of 1.5 to 2. The optimum temperature required by Pepsin in the human body is between 37°C and 42°C.