Partial purification and characterization of Chinook salmon (Oncorhynchus tshawytscha) calpains and an evaluation of their role in postmortem proteolysis

The involvement of calpains in the proteolysis of salmon muscle during refr igerated storage was investigated. Salmon m-calpain and (mu -calpain were p urified and partially purified, respectively. Salmon In-calpain had similar calcium requirements and specific activity against casein as ovine m-calpa in. Salmon mu -calpain had similar calcium requirements as ovine mu -calpai n but a lower specific activity against casein than ovine mu -calpain. Auto lysis patterns of both calpains differed from those of ovine calpains, and their activities were less than those of mammalian muscles. Calpastatin act ivity was relatively high and comparable to that of bovine muscles. Little proteolysis and fiber fragmentation resulted during refrigerated storage. H owever, proteolysis could be reproduced by incubation of myofibrils with m- calpain.