Proteinases from Gastric Mucosa of European Sheatfish, Silirus Glanis L.

Three proteinases (P1, P2, and P3) were isolated from the gastric mucosa of European sheatfish (Silurus glanis L.) by (NH₄)₂SO₄ precipitation, gel chromatography on Sephadex G-75, and ion-exchange chromatography on DEAE cellulose. Isoelectric focusing was used for determining the values of pI of the isolated proteinases, which were equal to 1.9, 3.2, and 4.75 (for P1, P2, and P3, respectively). The molecular weight of P1 was 39800 Da; P2 and P3 had equal molecular weights of 30200 Da each. The optimum pH for the three peptidases isolated from sheatfish gastric mucosa and the maximum stability of these enzymes were found to be at acidic pH. This allowed identification of these proteinases as pepsin-type enzymes of fish.