PURIFICATION AND CHARACTERIZATION OF ACIDIC PROTEASES FROM THE STOMACH OF THE DEEP-WATER FINFISH ORANGE ROUGHY (HOPLOSTETHUS-ATLANTICUS)

Acidic proteases were extracted and purified from the stomach of orang e roughy (Hoplostethus atlanticus). Protease I and II were glycoprotei ns with molecular weights of 33.5 and 34.5 KDa, respectively, Protease I had an isoelectric point of 5.30. The two forms of protease II (a a nd b) had isoelectric points of 4.35 and 4.40, respectively, and N-ter minal sequence identity for 12 amino acids. The proteases exhibited op timal temperature activity at 37C. They had high activity at low tempe ratures and low thermal stability compared to mammalian pepsins, They were stable in the pH range of 2-4.5 and unstable above pH 6.5, Protea se I and II had pH optima of 2.5 and 3.5, respectively, and K-m, value s for the hydrolysis of hemoglobin (pH 3.0, 37C) of 124 mu M and 517 m u M, respectively. Enzyme activities were inhibited by pepstatin A and high NaCl concentrations, and were slightly stimulated by Ca2+ and Cu 2+.