Pepsin A-4

Pepsin A-4 is one of the isoforms of pepsin, a powerful aspartic endopeptidase enzyme that is predominantly responsible for initial protein digestion in the human stomach.[1][3][5][8][9] Pepsin is secreted as deactivated pepsinogen by gastric chief cells and becomes activated in the acidic (pH 1.5–2.0) environment of gastric juice.[3] Pepsin cleaves peptide bonds within proteins, especially at sites adjacent to aromatic amino acids, yielding smaller peptide fragments for subsequent digestion and absorption in the small intestine.[2][3][9] In the context of disease, pepsin can contribute to tissue injury when present outside the stomach, particularly in conditions with abnormal reflux such as GERD and LPR, where it serves both as a pathogenic factor and a diagnostic biomarker.[1][4] Multiple isoforms (pepsin A-1, A-2, A-3, and A-4) are produced by pepsinogen gene subtypes; these are collectively referred to as “Pepsin A.”[8] There is nothing unique about a therapeutic role for Pepsin A-4 as a target; it is not specifically targeted by any approved drugs, nor is it a current focus for drug development or inhibition outside research settings. The main clinical use is in the context of laboratory diagnostics (salivary pepsin as a biomarker) and as a component of enzyme supplements for certain digestive disorders.[4][6] Note on entry: "Pepsin A-4" refers to a specific isoform within the pepsin family (pepsinogen 4); pepsin itself is an established enzyme, but "Pepsin A-4" is not widely recognized as a distinct therapeutic target entity. Most medical and scientific sources refer to “Pepsin A” or simply “Pepsin.” Therefore, this specific target designation ("Pepsin A-4") may represent an over-specific or under-standardized name in most biomedical databases, and use of the more general “Pepsin A” or “Pepsin” is advised for canonical forms in structured data.[8][4][9]

Other names

Pepsin 4Pepsinogen 4Pepsinogen A4Pepsin APepsinEC 3.4.23.1

Catalyzes the breakdown of proteins by hydrolyzing peptide bonds, leading to the production of smaller peptides and amino acids[1][2][5] Pepsin inhibitors like pepstatin act by occupying the active site and mimicking substrate interactions[5]