Characterization of Alkaline phosphatase (E.C.3.1.3.1) from freshwater Fish Species (Coptodon zillii, Heterobranchus bidorsalis, Clariasgariepinus and Chrysichthys nigrodigitatus)

Abstract

Alkaline phosphatases (APs) are homodimeric enzymes that catalyze the hydrolysis and transphosphorylation of phosphate monoesters. These enzymes help to modulate and remove the phosphate group from a protein. In this study, alkaline phosphatase activity was determined in different tissue homogenates (flesh and bones) of species four fish species - Coptodon zillii, Heterobranchus bidorsalis, Chrysichthys nigrodigitatus and Clarias gariepinus. The bone was found to have the highest activity of alkaline phosphatase. The Km and Vmax values for the fishbone alkaline phosphatase (FBAP) were estimated to be 0.0106mM and 2.1730 μmol/min/mol for C. zillii, 0.0074mM and 3.1868 μmol/min/mol for H. bidorsalis, 0.0226mM and 8.9928 μmol/min/mol for C. gariepinus and 0.0104mM and 6.0753 μmol/min/mol for C. nigrodigitatus respectively. The pH optimum of the enzyme for the categories of fish was estimated to be 9.0. Divalent metals such as Mg2+ and Ca2+ enhanced enzyme activity but have an inhibitory effect at concentrations above 1.5 mM. The highest activity of the enzyme in the bone of the four species of fishes in this study suggests that most of the organic phosphates in the species are hydrolysed principally in this tissue.