Sea cucumber is an important economic aquatic product in China. In this study, water extract in the body wall of Apostichopus japonicus was obtained by homogenization and water extraction. The protein and polysaccharide content in the water extract was(41.03 ± 1.97)% and (36.50 ± 1.58)%, respectively. Proteomics revealed that the water extract contained more than 400 types of protein molecules, majorly including yolk protein, tropomyosin and actin. Monosaccharide composition analysis and nuclear magnetic resonance spectroscopy analysis confirmed that the polysaccharide in the water extract was mainly sulfated fucan (FUC) with a molecular weight of (5 172.5 ± 107.6) kDa; various denaturants were used to destroy possible molecules in the water extract between them. It was found that the molecular weight of FUC did not change significantly before and after treatment, suggesting that FUC existed in a non-aggregated form. This study identifies for the first time the molecular types of proteins and polysaccharides in the water extract of the sea cucumber body wall, which could provide theoretical guidance for the subsequent optimization of sea cucumber processing techniques and reduction of the nutrient loss during the processing.
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