Enzymatic properties of a protease from the hepatopancreas of shrimp, Penaeus orientalis

The protease purified from hepatopancreas of shrimp, Penaeus orientalis, ha d high proteolytic activity in the pH range of 7.0 to 9.5. Temperature opti mum for hydrolysis of casein was 70C. The protease was stable at neutral an d alkaline pH and unstable at acidic pH. The apparent Michaelis-Menten cons tant (K-m) and the turnover number (V-max) of the protease on hydrolysis of N-CBZ-L-tyrosine p-nitrophenyl ester (CBZ-Tyr-NE) and N-CBZ-L-phenylalanin e p-nitrophenyl ester (CBZ-Phe-NE) were similar, however, those for N-CBZ-L -cysteine p-nitrophenyl ester (CBZ-Cys-NE) were different. K-m and V-max fo r hydrolysis of casein by the protease were determined to be 0.31% and 5.21 s(-1), respectively. The N-terminal sequence of the protease showed higher homology with the collagenase of crab and trypsins from crustacea. Myosin h eavy chain (MHC) was the primary substrate during proteolysis with the prot ease. Actin/tropomyosin were degraded progressively during 2 h incubation b ut to a lesser extent than MHC.