Characterization of human pepsin II obtained from purified gastric pepsinogen II.

Human pepsinogen II (PgII) was purified from human gastric mucosa by immunoadsorbents using anti-PgII antiserum. Contaminating pepsinogen I (PgI) was adsorbed by a subsequent anti-PgI immunoadsorbent. PgII was further purified on DEAE-Sphadex A50. By agar gel enzyme electrophoresis (AEE) at pH 8.2 PgII was separated into five proteolytic bands, demonstrated upon acidification and incubation with hemoglobin. PgII was converted to pepsin II (PII) by acidification at pH 2.0 and was immediately separated from its inhibitory peptide and from other substances by DEAE chromatography. Purified PII showed two bands in AEE at pH 5.6 and was immunochemically identical with PgII. The "gastricsin" and "pepsin" purified from acid gastric juice by classical procedures proved to be identical with PII and pepsin I (PI), respectively. PII showed a broad pH range with one maximum at pH 2.9. PII in contrast to PI did not hydrolize N-acetylphenylalanyl-3,5-diiodotyrosine and proved to be more alkali-stable than PI. A modified nomenclature is proposed for the human pepsinogen system.