Partial purification and characterization of digestive acidic and alkaline proteases from the visceral waste of grass carp, Ctenopharyngodon idella (Valenciennes, 1844)

Abstract

Acidic and alkaline proteases from visceral waste of Ctenopharyngodon idella (Valenciennes, 1844) were isolated, partially purified by ammonium sulphate precipisstation followed by dialysis, their kinetics and characteristics studied. The crude enzyme was partially purified and its molecular weight was studied. The enzyme showed highest activity and purification-fold when precipitated at 40–60% ammonium sulfate. The purification fold increased from 1.23 to 2.49 and 1.17 to 1.51 in acidic and alkaline protease respectively along the purification steps. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed a molecular weight of 15-35 kDa and 25-63 kDa respectively in acidic and alkaline proteases. The pH and temperature optima for acidic and alkaline proteases were 3 and 10, at 40 °C and 60 °C respectively. The acidic and alkaline protease activity was decreased by 40% and 60%, when incubated at 90 °C for 30 min. Degree of hydrolysis (DH) of the proteases on muscle protein increased with increase of enzyme concentrations. The study showed that proteases from Grass carp visceral waste of could find use in applications where maximum activity at moderate temperature is desired.