Purification and Properties of Proteases from Tilapia Intestine

Abstract

Two proteolytic enzymes designated as PA-3 and PB-3 were obtained from the intestine of Tilapia nilotica. These enzymes were purified by precipitation with ammonium sulfate and by chromatographies on trypsin inhibitor-Sepharose 4B, DEAE-cellulose, Polybuffer exchanger (PBE 94), and Sephadex G-100, up to the specific activity of 260 and 350-fold, respectively.
PA-3 and PB-3 had molecular weights of 32, 000 and 21, 000, respectively, and showed the highest activity at 55°C and at a pH of 8.5-9.0. They were stable at pH 7.0-10.5 and below 50°C.
The K_m values for casein of two enzymes were calculated to be 0.03mg/ml.
The effect of various inhibitors on enzyme activities was examined and as a result, it was presumed that PA-3 was a serine protease and that PB-3 was a cysteine protease.