Pepsinogen A-4 (PGA4)

Pepsinogen A-4 (PGA4) is a proenzyme (zymogen) form of the digestive enzyme pepsin, a member of the aspartic protease (peptidase A1) family, synthesized and secreted by gastric chief cells in the stomach[1][6][3]. In the highly acidic environment of the stomach, PGA4 is activated (by proteolytic cleavage) to form pepsin A, which hydrolyzes dietary proteins into peptides[2][3]. Pepsinogen A subtypes, including PGA4, are essential for initiating protein digestion. There are several pepsinogen A isoforms (PGA3, PGA4, PGA5), all encoding essentially the same enzyme[1][2][6]. Expression of PGA4 is primarily in gastric mucosa, and its serum levels can reflect gastric mucosal health[5][6]. Elevated or diminished pepsinogen A levels are clinically relevant as non-invasive biomarkers for gastric atrophy and increased cancer risk[2]. Although a key enzyme in digestion, pepsin A/PGA4 is not considered a conventional drug target and is not the focus of therapeutic drug development. Some compounds, such as pepstatin and sucralfate, can inhibit its function in vitro or as part of anti-ulcer therapy[2][3].

Other names

Pepsin A-4PGA4Pepsinogen-4Pepsin APepsinogen 4Group I (pepsinogen A)Pregnancy-associated glycoprotein

Protease inhibition (by pepstatin: competitive, reversible inhibition of active site)