Changes of collagen in sea cucumber (Stichopus japonicas) during cooking

Xiuping Dong, Beiwei Zhu , Liming Sun, Jie Zheng, Dan Jiang, Dayong Zhou, Haitao Wu, Yoshiyuki Murata

Abstract:

Changes of the collagen in sea cucumber (Stichopus japonicas) during cooking were investigated. Crude collagen fibers (CCF) is more sensitive to heat than pepsin-solubilized collagen (PSC), absorbance at 226–232 nm increased from 60 to 100°C. PSC nearly completely degraded after cooking for 8–10 h, 4–6 h, 1–1.5 h, 40–50 min, and 10–20 min at 60, 70, 80, 90, and 100°C, respectively. Collagen fiber shrinkage, disappearance of periodic cross striation, complete denaturation, and dispersion of denatured fibers at 40, 60, 80 and 100°C, respectively, were demonstrated by transmission electron microscope (TEM). Above results might be instructional for sea cucumber processing and collagen usage.

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Keywords:

sea cucumber (Stichopus japonicus), collagen, cooking

Purification and characterization of cathepsin B from the gut of the sea cucumber (Stichopus japonicas)

Li-Ming Sun, Bei-Wei Zhu , Hai-tao Wu, Lei Yu, Da-Yong Zhou, Xiuping Dong, Jing-Feng Yang, Dong-Mei Li, Wen-Xiu Ye and 1 more

Abstract

Cathepsin B from the gut of sea cucumber (Stichopus japonicas) was purified 81-fold with a 3% recovery by ammonium sulfate fractionation and a series chromatography on DEAE Sepharose CL-6B, Sephadex G-75, and TSK-Gel 3000 SWxl. The purified protein appeared as a single band on Native-PAGE but showed 2 bands of 23 and 26 kDa on SDS-PAGE. The optimum activity was found at pH 5.5 and 45°C. The enzyme was stable at pH 4.5–6.0 and the thermal stability was up to 50oC. The enzyme was strongly inhibited by E-64, iodoacetic acid, and antipain, demonstrating it is a cysteine protease containing sulfhydryl groups. Cu2+, Ni2+, and Zn2+ could strongly inhibit the enzyme activity. The amino acid sequences of the purified enzyme were acquired by mass spectrometer, which did not show any homology with previously described cathepsins, suggesting it may be a novel member.

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Keywords

cathepsin B,  sea cucumber (Stichopus japonicus),  purification,  characterization