Pepsinogens and pepsins from mandarin fish (Siniperca chuatsi)

Four pepsinogens (PG-I, PG-II, PG-III(a), and PG-III(b)) were highly purified from the stomach of the freshwater fish mandarin fish (Siniperca chuatsi) by ammonium sulfate fractionation, anion exchange, and gel filtration. The molecular masses of the four purified PGs were 36, 35, 38, and 35 kDa, respectively. All the pepsinogens converted into their active form pepsins within a few minutes under pH 2.0. The optimum pH and temperature of the four enzymes were 3.0-3.5 and 45-50 degrees C, using hemoglobin as a substrate. The N-terminal amino acid sequences of PG-I and PG-II were determined to the 12th and 17th amino acid residues, respectively. Western blot analysis using antisea bream polyclonal antibodies cross reacted with PG-I, PG-II, and PG-III(b) while no cross reaction with PG-III(a) was detected, suggesting the diversity of pepsinogens in fish.