Zi-Qiang Liu1, Yu-Xin Liu1,2, Da-Yong Zhou1,2, Xiao-Yang Liu1,2, Xiu-Ping Dong1,2, Dong-Mei Li1,2, Fereidoon Shahidi3. 1. School of Food Science and Technology, Dalian Polytechnic University, Dalian, P. R. China. 2. National Engineering Research Center of Seafood, Dalian, P. R. China. 3. Department of Biochemistry, Memorial University of Newfoundland, St John's, Canada.
Abstract
BACKGROUND: Sea cucumber (Stichopus japonicus) is easy to autolysis in response to a variety of environmental and mechanical factors. In the current study, collagen fibres were extracted from fresh sea cucumber body wall and then incubated with endogenous matrix metalloprotease (MMP) of sea cucumber. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), chemical analysis and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis were utilized to demonstrate the changes in collagen fibres, collagen fibrils and collagen proteins. Moreover, a verification experiment was also carried out to confirm the contribution of MMP to the autolysis of sea cucumber. RESULTS: Endogenous MMP caused complete depolymerization of collagen fibres into smaller collagen fibril bundles and collagen fibrils due to the fracture of proteoglycan interfibrillar bridges. Meanwhile, endogenous MMP also caused partial degradation of collagen fibrils by releasing soluble hydroxyproline and pyridinium cross-links. Furthermore, the treatment with MMP inhibitor (1,10-phenanthroline) prevented the autolysis of tissue blocks from S. japonicus dermis. CONCLUSION: Endogenous MMP was the key enzyme in the autolysis of sea cucumber, while its action still focused on high-level structures of collagens especially collagen fibres.
BACKGROUND: Sea cucumber (Stichopus japonicus) is easy to autolysis in response to a variety of environmental and mechanical factors. In the current study, collagen fibres were extracted from fresh sea cucumber body wall and then incubated with endogenous matrix metalloprotease (MMP) of sea cucumber. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), chemical analysis and sodium dodecyl sulphatepolyacrylamide gel electrophoresis (SDS-PAGE) analysis were utilized to demonstrate the changes in collagen fibres, collagen fibrils and collagen proteins. Moreover, a verification experiment was also carried out to confirm the contribution of MMP to the autolysis of sea cucumber. RESULTS: Endogenous MMP caused complete depolymerization of collagen fibres into smaller collagen fibril bundles and collagen fibrils due to the fracture of proteoglycan interfibrillar bridges. Meanwhile, endogenous MMP also caused partial degradation of collagen fibrils by releasing soluble hydroxyproline and pyridinium cross-links. Furthermore, the treatment with MMP inhibitor (1,10-phenanthroline) prevented the autolysis of tissue blocks from S. japonicus dermis. CONCLUSION: Endogenous MMP was the key enzyme in the autolysis of sea cucumber, while its action still focused on high-level structures of collagens especially collagen fibres.