The partitioning of protease from Calotropis procera latex by aqueous two-phase systems and its hydrolytic pattern on muscle proteins

The protease from the latex of Calotropis procera was isolated by an aqueous two-phase system (ATPS). Polyethylene glycol (PEG 1000, 2000 and 3000) at a concentration of 12, 15, and 18% (w/w) with salts ((NH4)2SO4, K2HPO4 and MgSO4) at a concentration of 14, 17, and 20% (w/w) were investigated. The highest protease recovery (74.6%) was found in the PEG-rich phase of the system (p < 0.05), comprising of 18% PEG 1000 and 14% MgSO4. Protein patterns and activity staining showed that the isolated protease had a molecular weight of ∼31 kDa without the oligosaccharide attached to the molecule. Degradation of muscle proteins in beef, farmed giant catfish, and squid was observed by the electrophoresis of sodium dodecyl sulphate polyacrylamide gel (SDS-PAGE). The degradation of myofibrillar proteins (myosin heavy chain: MHC and actin: AC) of farmed giant catfish was higher than that of beef and squid muscles as indicated by the degradation proteins with lower molecular weight.