Cleavage sites and non-enzymatic self-degradation mechanism of ready-to-eat sea cucumber during storage

The non-enzymatic degradation of ready-to-eat sea cucumber (RSC) was closely related to the quality of sea cucumber products. When stored at 37 degrees C for 0-30 d, the hardness of RSC decreased by 86.7% and the proportion of free water increased by 12.71%. The content of free hydroxyproline increased from 8.33 mu g/g to 24.12 mu g/g. Label-free quantitative proteomics analysis showed that protein was prone to break at the sites of G, Q, N, D, and L, and the peptide bonds in QI, DL, NL, RI, EF and SY were much more liable to break. Edman degradation method showed that the breakage sites of RSC were at S, D, H, E, and V. NL, NA and NG calculated by B3LYP/631G(d) showed that the relative free energies in the initial cyclization step were 53.20, 143.53 and 78.10 kcal/ mol, respectively, which may be the rate-determining step for peptide bond cleavage.

Automated summary

The non-enzymatic degradation of ready-to-eat sea cucumber products is closely related to their quality, as indicated by decreased hardness, increased free water content, and higher levels of free hydroxyproline. Protein was found to break easily at specific sites, with certain peptide bonds being more susceptible to cleavage, while the relative free energies of specific steps determined the rate of peptide bond cleavage.