Characterisation of alkaline phosphatase from hepatopancreas and intestine of red tilapia (Oreochromis spp.) from Malaysia

Abstract

Alkaline phosphatase (ALP) is an enzyme typically found in the liver and intestines of many organisms. High levels of ALP in a fish, indicate that the fish is either sick or has been exposed to heavy metals. In this study, ALP was purified from the hepatopancreas and intestine of red tilapia (Oreochromis spp.) using two main steps: ammonium sulphate precipitation and ion-exchange chromatography. Samples from the ion exchange step were analysed for ALP activities and characterized using SDS-PAGE. The SDS-PAGE analysis revealed two identical bands with ALP molecular weights of 68,000 Da (hepatopancreas) and 180,500 Da (intestine) components. Overall, the hepatopancreas and intestine purification folds acquired from the final step were 1.8 and 21.9, respectively, with recovery of only 0.22% (hepatopancreas) and 0.01%. (intestine). From the hepatopancreas and intestine, the specific activity of the enzyme was 1.72 X 10-2 mol-1 mg-1 and 2.93 X 10-1 mol-1 mg-1, respectively. ALP from the hepatopancreas was stable up to 50°C, while the optimal temperature for intestine enzyme ALP was 60°C. The ideal pH for ALP of Oreochromis spp.’s hepatopancreas and intestine was pH 10. The Li+, Na+, and K+ positive monovalent alkali metal ions have no impact on the action of the ALP enzyme. However, the enzyme actions are triggered by the positive divalent alkaline metal ions Mg2+ and Ca2+. The heavy metal ions, Zn2+, Cu2+, Cd2+, and Hg2+, were discovered to inhibit the action of the ALP enzyme. Overall, the identification of ALP would be helpful as a diagnostic instrument for determining the health and quality of fish.