Pepsin, an acid protease, contains a proteolytic enzyme. Pepsin contains the 'cathepsin' component which has milk curdling activity. It has a broad range of substrate activity and demonstrates an esterase acitivity. It generally attacks peptide bonds.

• Presentation: Off-White Powder
• Extinction Coefficient (E1%): E1%280 = 14.7
• Isoelectric point (pI): pH 1.0
• Optimum pH 1 to 3.5, untable above pH 6.0
• Freely soluble in water; dissolves readily in 0.01 M HCl (0.5 mg/ml - clear, colorless solution); practically insoluble in alcohol, chloroform or ether.

Pepsin is a peptidase used to digest proteins and is commonly used in the preparation of Fab fragments from antibodies. Pepsin, from porcine gastric mucosa, has been used to hydrolyze dry cervical samples in mice.

Pepsin hydrolyzes peptide bonds, not amide or ester linkages. Pepsin cleaves peptides with an aromatic acid on either side of the peptide bond. Sulfur-containing amino acids increase susceptibility to hydrolysis when they are close to the peptide bond. Pepsin preferentially cleaves at the carboxyl side of phenylalanine and leucine and at the carboxyl side of glutamic acid residues. Cleaves Phe-Val, Gln-His, Glu-Ala, Ala-Leu, Leu-Tyr, Tyr-Leu, Gly-Phe, Phe-Phe and Phe-Tyr bonds in the β chain of insulin. Pepsin is the major proteolytic enzyme produced in the stomach. It digests proteins through the cleavage of interior peptide linkages.