Proteolysis of skeletal muscle in yellowfin tuna (Thunnus albacares): Evidence of calpain activation

Abstract

Abstract 1. 1. White muscle of yellowfin tuna is subject to a form of deterioration known as “burnt tuna”. 2. 2. TEM and SDS-PAGE were used to quantify cellular differences in deteriorated white muscle of yellowfin tuna. 3. 3. Electron micrographs showed a significant loss of Z-disc integrity and an increase in intracellular edema in burnt tuna. 4. 4. Electrophoresis established that a specific doublet of proteins, 42 kD and 46 kD was lost. 5. 5. Proteolysis of isolated myofibrils incubated in calpain (EC 3.4.22.17) was greatest at pH 7.5 and was selective for intermediate molecular weight proteins. 6. 6. This evidence suggests that burnt tuna is a specific and limited proteolysis of myofibrillar structural proteins characteristic of calpain proteolysis.