Comparative study on proteolysis of two species of bigeye snapper, Priacanthus macracanthus and Priacanthus tayenus

Proteolytic activity in muscle from two species of bigeye snapper (Priacanthus macracanthus and Priacanthus tayenus) was studied. Autolysis of mince and washed mince at SO and 60degreesC was compared. Higher degradation of myosin heavy chain was observed in both mince and washed mince from P macracanthus than in those from P tayenus, especially when the incubation time was increased. Autolysis of washed mince from both species was inhibited by soybean trypsin inhibitor, suggesting that myofibril-associated proteases were serine proteases. When sarcoplasmic proteolytic activity in P macracanthus muscle was studied, two activity peaks with an optimum temperature of 60degreesC were observed at pH 6.5 and S. S. The activities of both peaks were mostly inhibited by soybean trypsin inhibitor, suggesting that the major protease was a serine protease. Major sarcoplasmic proteolytic activity in P macracanthus muscle was found at M-r 62 000 on sodium dodecyl sulphate substrate gel. For P tayenus sarcoplasmic proteolytic activity, two activity peaks with an optimum temperature of 60degreesC were found at pH 5.0 and 8.5. The pH 5.0 peak activity was effectively inhibited by pepstatin A, while the pH 8.5 peak activity was inhibited by several inhibitors. The results indicated that various sarcoplasmic proteases were present in P tayenus muscle. The two species contained different sarcoplasmic proteases in terms of composition and activity level. P macracanthus muscle generally had higher sarcoplasmic proteolytic activities than P tayenus muscle. (C) 2003 Society of Chemical Industry.