Abstract: Myofibril-bound serine proteinase (MBSP) in the skeletal muscle of silver carp has been characterized. Myosin heavy chain (MHC) degraded markedly when silver carp myofibril was incubated at 55～60℃ as shown by SDS-PAGE. Prolonged incubation of myofibril also caused the degradation of other myofibrillar proteins such as α-actinin, actin and tropomyosin to some degree. The results suggested the existence of an endogeneous myofibril associated proteinase. Serine proteinase inhibitors (Pefabloc SC and Lima bean trypsin inhibitor) and EDTA greatly suppressed the degradation of myosin heavy chain, while inhibitors for cysteine, and asparatic proteinases did not show any effect. These effects indicated that the endogeneous proteinase was a myofibril-bound serine proteinase (MBSP) that needed metal ion(s) for activation.

Key words: myofibril, serine proteinase, degradation, inhibitor, Western blot