Purification and Characterization of an Alkaline Protease From the Viscera of Bolti Fish (Tilapia Nilotica)

Abstract

An alkaline protease was extracted from acetone powder of the viscera of bolti fish (Tilapia nilotica) with distilled water, precipitated from the extract by 40–60% (NH4)2SO4and then dialyzed. Enzyme homogeneity studies by polyacrylamide gel electrophoresis (PAGE) illustrated that the enzyme was homogenous. Sodium dodecyl sulfate–PAGE showed a molecular weight of 23.0 kDa. The optimal pH and optimal temperature were 8.0 and 45C, respectively, with casein as a substrate. A remarkable stability was observed under alkaline conditions (pH 6.0–10.0), where more than 90% of the enzyme activity was maintained. In the acidic region (pH 2.0–6.0), the enzyme retained more than 50% of its activity. Furthermore, the enzyme retained 85.4 and 41.8% of its activity after heating at 50 and 60C for 120 min, respectively, while the relative activity after heating at 70C for 120 min was 5.25%. The alkaline enzyme lost most of its activity when incubated at 80C for 30 min. A high percentage of total enzyme activity was inhibited when the enzyme was incubated with 50 mM of either soybean trypsin inhibitor or ethylenediaminetetraacetic acid. The presence of NaCl and CaCl2at 10 mM concentration increased the enzyme activity by 6.9 and 10.6%, respectively.

Effect of dietary protein source and time on alkaline proteolytic activity of Nile tilapia (Oreochromis niloticus)

“…Our results are in agreement with the previous observations reported, in spite of the fact that tilapia is an omnivorous fish species, with predominantly herbivorous feeding habits. Trypsin-like enzymes have been identified in tilapia (Bezerra et al 2005;El-Beltagy et al 2005). However, the relative contribution of specific proteases to the overall alkaline proteolytic activity was not assessed in this study and should be considered in further research.…”

Proteinases from the Liver of Albacore Tuna (Thunnus Alalunga): Optimum Extractant and Biochemical Characteristics

“…Alkaline proteases from the red scorpionfish (Scorpaena scrofa) viscera exhibited optimal activity at pH 10.0 and 55C (Younes et al 2014). The optimal pH and temperature of alkaline protease from the viscera of bolti fish (Tilapia nilotica) were 8.0 and 45C, respectively, with casein as a substrate (El-Beltagy et al 2005). The optimum pH and temperature of serine protease from the viscera of sardinelle (Sardinella aurita) were around pH 8.0 and 60C, respectively (Ben et al 2011).…”

Purification and Characterization of Trypsin From Pyloric Caeca of Bigeye Snapper (Pricanthus Macracanthus)

“…(2004) found that the molecular weight of isolated trypsin from the pyloric caeca of Monterey sardine was 25 kDa. El‐Beltagy et al. (2005) reported that purified alkaline protease from the viscera of Bolti fish had a molecular weight of 23 kDa.…”