Purification and characterization of a myofibril-bound serine proteinase from the skeletal muscle of silver carp

Recently, a myofibril-bound serine proteinase (MBSP) in the skeletal muscle of silver carp was identified. MBSP could be dissociated from myofibrils by treatment at pH 4.0. Following ultrafiltration concentration and chromatography on Sephacryl S-200, High Q ion-exchange and affinity column of Arginine Sepharose-4B, MBSP was partially purified. The enzyme with an estimated molecular weight of 28 kDa cleaves synthetic fluorogenic substrates specifically at the carboxyl sites of arginine and lysine residues. MBSP activity is suppressed by serine proteinase inhibitors such as Pefabloc SC, lima bean trypsin inhibitor and benzamidine; it is insensitive to Pepstatin, L-3-carboxy-trans-2, 3-epoxypropionyl-L-leucine-4-guanidinobutylamide and ethylenediaminetetraacetic acid, suggesting MBSP is a trypsin-like serine proteinase. Optimal profiles of pH and temperature of the enzyme are 8.5 and 55C, respectively. Hydrolysis of myofibrillar proteins such as myosin heavy chain, actin and tropomyosin by purified MBSP occurred especially at around 55C, consistent with our proposal that MBSP plays a significant role in the Modori phenomenon.