Contribution Of Endogenous Enzymes To Protein Degaradation In The Autolysis Of Sea Cucumber Stichopus Japonicus Body Wall

Sea cucumber is an important marine invertebrate, and shows high nutritional values. However, sea cucumber possesses strong ability of autolysis, which leads to huge economic losses.The contribution of endogenous proteases to autolysis of sea cucumber Stichopus japonicus muscle tissues(sj MTs) were investigated. The optimal condition of autolysis conditions of sj MTs were determined by treatment with UV irradiation and heating. The proteins removed from sj MTs were analysed by SDS-PAGE and TCA-soluble oligopeptide assay. The results showed that the proteins removed from sj MTs were mainly myosin heavy chains(MHC), paramyosin and actin, respectively. Under the proteolysis condition of p H5 and p H6 at 50 ℃, the muscle tissues degradation phenomenon is obvious at 3h. At this condition, the effects of cysteine and serine protease inhibitors, including iodoacetic acid(IA), trans-epoxysuccinyl-L-leucyl-amido(4-guanidino) butane(E-64), antipain(AP), phenylmethanesulfonyl fluoride(PMSF), tosyl-phenylalanine chloromethyl-ketone(TPCK) and tosyl-l-lysine chloromethyl Ketone(TLCK)on sj MTs degradation were further studied. The results showed that all the inhibitors indicated the inhibitory effect on autolysis of sj MTs. These results suggest that cysteine and serine proteases are partially involved in the proteolysis of muscular proteins of sea cucumber Stichopus japonicus.The effect of sea cucumber intestine collagenase on sea cucumber pepsin-solubilized collagen(PSC) degradation was also studied. The optimal conditions of activity of sea cucumber intestine collagenase were at p H9 and 40℃. PSC can be degraded effectively by sea cucumber intestine collagenase with the decrease of band intensity of PSC and increase of TCA-soluble oligopeptide content. These results suggest that sea cucumber intestine collagenase may be involved in collagen degradation in the process of autolysis.