Contribution Of Endogenous Enzymes To Autolysis Of Sea Cucumber Stichopus Japonicus Guts And Antioxidant Activities Of Oligopeptides

In general, sea cucumber guts were discarded as waste in our country, causing not only nutrients loss, but also environmental pollution. Sea cucumber possesses strong ability of autolysis, which leads to severe deterioration in its quality during processing, storage and transport.The effect of endogenous enzymes on autolysis of sea cucumber Stichopus japonicus guts was studied by addition of protease inhibitors and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).The results of SDS-PAGE indicated that TLCK, E-64, antipain had almost complete inhibitory effects on the protein degradation of sea cucumber S. japonicus guts, whereas TPCK and pepstain showed partially inhibitory effects. These results suggest that serine and cysteine proteases play the major role in autolysis of sea cucumber S. japonicus guts, while pepsin have weak effect on the autolysis of sea cucumber S. japonicus guts.In addition, the antioxidant activities of oligopeptides (Val-Gly-Thr-Val-Glu-Met, Val-Thr-Pro-Tyr) from sea cucumber S. japonicus guts were studied on the basis of the previous study. The antioxidant activities of oligopeptides from sea cucumber S. japonicus guts were evaluated by measuring the scavenging abilities on hydroxyl radical, superoxide radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical using an ESR spectrometer. The results showed that two kinds of oligopeptides from sea cucumber S. japonicus guts had scavenging abilities on ·OH、O2-·and DPPH in a dose-dependent manner. The scavenging ability of Val-Gly-Thr-Val-Glu-Met was significantly higher than that of Val-Thr-Pro-Tyr at different concentrations (p<0.05).Furthermore, the influence of oligopeptides on H2O2-induced oxidative damage in Jurkat and HL-60 cells was also investigated. Results showed that the relative survival rate of cells decreased with the increasing concentration of H2O2. The results of DNA ladder showed that the oligopeptides failed to protect the DNA oxidative damage induced by H2O2 at low concentrations, but induced synergistically cell death with H2O2 at high concentration. The mechanism involved in this action remains to be further studied.