Pepsinogen I/II (PGI/II)

Changes in pepsinogen (PG) are biological indicators of gastric cancer precursors, and gastric mucosal carcinogenesis is closely related to the amount of secretion of PG.PG has an isoelectric point of 4.13, is an acidic protein with a total length of 373 amino acid residues, and a molecular weight size of 40,306.05 (about 42 kDa). As a precursor substance of pepsin, PG is an aspartic acid protease with digestive function, a single-chain polypeptide consisting of 375 amino acids, which is mainly secreted by gastric cells, and is classified into 2 categories: pepsinogen I (PGI) and pepsinogen II (PGII), which is based on the difference in mobility under agar gel electrophoresis. There are a total of seven isoforms, pgl-pg7, of which pgl-pg5 have a common immunogenicity and are collectively referred to as PG I; pg6 through pg7 are referred to as PG II.

As substances secreted by cells in association with digestion, the cellular origin and tissue distribution of PG I and PG II vary within tissues. Most of the pepsinogen enters the gastric lumen and is converted into pepsin, thus completing the digestive function. Only 1% of pepsinogen enters the blood circulation through the capillaries of the gastric mucosa and exists stably, and the secretion of pepsinogen is altered in the case of gastric atrophy. Therefore, serum levels of PGI and PGII can be used as a reliable indicator of gastric mucosal atrophy. In atrophic gastritis, PG secretion decreases because of decreased secretory capacity.PGI is secreted by the principal cells of the gastric body, and gastric mucosal atrophy decreases the level of serum PGI expression.PGII is secreted in the mucosa of the gastric antrum and the gastric body, and when the whole gastric mucosa atrophies, the level of PGII decreases. As gastric mucosal atrophy increased, PG I and PG I/PG lI ratio decreased.

KMD Bioscience, as a supplier of in vitro diagnostic raw materials, provides the IVD industry with high quality diagnostic antigens and antibodies for flow, colloidal gold, chemiluminescence, immunoturbidimetric and other assay platforms for over several years.

The inventory of reagents associated with Pepsinogen I (PGI) that KMD Bioscience can offer:

Pepsinogen Synthesis

In the stomach, the primary cells of the gastric mucosa first release pepsinogen, the inactive precursor of pepsin, whose spatial structure is dominated by α-helical and β-folded structures. Pepsinogen is activated in an acidic environment by breaking an amino acid sequence (containing about 44 amino acid residues) from the N-terminus, which transforms it into active pepsin.

The two pepsinogens, PGI and PGII, have two distinct sets of biochemical properties. They differ in the pH at which they are activated, with the optimal pH being 1.5-2.0 for PG I and 3.2 for PG II. In addition, PG I is more sensitive to alkaline-generated denaturation than is PG II. Both PG I and PG II become inactive at pH >5, and irreversible denaturation occurs at pH >7.2 or at temperatures greater than 65 °C. Activated pepsinogen acts to hydrolyze proteins, mainly hydrolyzing amino acids composed of residues such as phenylalanine, tyrosine, methionine, or leucine, and also acting on peptide chains composed of glutamic acid.

Biological significance of PGI and PGII

PGI, PGII and PGI/PGII ratio are associated with atrophic gastritis, while low PGI levels (≤70 ng/mL) and PGI/PGII ratio (≤3) are often found in gastric cancer. Therefore, simultaneous detection of PGI and PGII is important for early diagnosis and treatment of cancer. The lower the serum PGI/PGII ratio, the higher the incidence of gastric cancer. Combined measurement of serum PGI and PGII levels and their ratio can serve as a "serologic biopsy" of the gastric mucosa.

KMD Bioscience has many years of experience in the research of antibody drugs, and owns four platforms: monoclonal antibody production platform, polyclonal antibody production platform, phage antibody library technology platform, and antibody sequencing and application platform, and is committed to the rapid development and large-scale production of in vitro diagnostic proteins and antibodies. At the same time, KMD Bioscience is always looking for newer targets and is committed to providing customers with diversified antibody products. KMD Bioscience can create customized one-stop solutions for customers according to their needs and application scenarios, fully supporting the development of in vitro diagnostic reagent products.