• Fisheries and Aquatic Sciences
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• v.21 no.5
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• pp.13.1-13.8
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• 2018

Amyloid plaque, also called senile plaque, the product of aggregation of ${\beta}$-amyloid peptides ($A{\beta}$), is observed in brains of the patients with Alzheimer's disease (AD) and is one of the key factors in etiology of the disease. In this study, hydrolysates obtained from the sea hare (Aplysia kurodai) were investigated for ${\beta}$-secretase inhibitory peptide. The sea hare's muscle protein was hydrolyzed using six enzymes in a batch reactor. Trypsin hydrolysate had highest ${\beta}$-secretase inhibitory activity compared to the other hydrolysates. ${\beta}$-secretase inhibitory peptide was separated using Sephadex G-25 column chromatography and high-performance liquid chromatography on a C18 column. ${\beta}$-secretase inhibitory peptide was identified as eight amino acid residues of Val-Ala-Ala-Leu-Met-Leu-Phe-Asn by N-terminal amino acid sequence analysis. $IC_{50}$ value of purified ${\beta}$-secretase inhibitory peptide was $74.25{\mu}M$, and Lineweaver-Burk plots suggested that the peptide purified from sea hare muscle protein acts as a competitive inhibitor against ${\beta}$-secretase. Results of this study suggest that peptides derived from sea hare muscle may be beneficial as anti-dementia compounds in functional foods or as pharmaceuticals.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.1
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• pp.66-78
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• 2023

The sea hare Aplysia kurodai is an economic species located along the Korean coast. This study aimed to investigate the stomach contents of A. kurodai and its relationship with marine algal flora surrounding their habitat. A. kurodai and marine algae were sampled in seven and five areas in the East and the South seas, respectively. The marine algae found in the stomach and surrounding marine habitat were identified. In the East Sea of Korea, 134 species of seaweed were recorded. Thirty-nine species of marine algae were identified in the stomach contents of A. korudai collected from the East Sea of Korea. Seventy-five species of seaweed were collected in the South Sea of Korea. In addition, 26 species of marine algae were identified in the stomach contents of A. kurodai from the South Sea of Korea. Among the stomach contents of A. kurodai, ten sheet,12 filamentous, 27 coarsely branched, and one jointed calcareous form species were identified.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.6
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• pp.550-556
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• 1985

In order to evaluate the marine mollusc muscle as foodstuff not only from the biochemical aspect but also from the view point of food science, we have analyzed the protein and amino acid compositions of the echiurid (Urechis unicinctus) and sea hare (Aplysia kurodai) muscle. The protein quality of the muscles was also investigated using in vitro methods based on in vitro digestibility, predicted digestibility, computed PER (C-PER) and discriminant computed PER(DC-PER). The remarkable feature of the protein compositions of the both muscles was that water soluble protein occupied a large amount of the muscle protein with fairly lower contents of the salt soluble protein. From the analysis of SDS-PAG electrophoresis, the sarcoplasmic proteins in the echiurid and the sea hare muscles were composed of 15 and 10 subunits, respectively. The free amino acid compositions of the total amino acids in the echiurid and sea hare muscle were characterized with $75\%$ of glycine and alanine, and with $78\%$ of taurine, respectively. The amino acid anaylsis of both muscle proteins showed that the echiurid muscle was rich in glycine, aspartic acid, glutamic acid, arginine and lysine, but was poor in cysteine, while the sea hare muscle was rich in glycine, glutamic acid, aspartic acid and arginine, but was negligible in cysteine and tryptophan. In the total amino acid profiles of the freeze dried muscles in echiurid and sea hare, there was not found a significant difference compared to the amino acid compositions of the muscle proteins. Predicting the protein quality of the echiurid and sea hare muscles using the in vitro method, it was apparently low compared to the muscle protein of fishes.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.1
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• pp.14-19
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• 2011

In this study, we extracted a whole polysaccharide fraction from the sea hare, Aplysia kurodai, and screened its functional properties using cell lines. The functionalities of polysaccharide and glycosaminoglycan (GAG) were investigated with RAW 264.7 cell lines. The crude polysaccharides and GAG purified DEAE-Sepharose chromatography did not show the toxicity on RAW 264.7 cell line in the range of $10\sim200{\mu}g$/mL, whereas they increased the cell growth rate. The crude polysaccharides and purified GAG also increased the production of NO, interleukin-6 and tumor necrosis factor-$\alpha$ on RAW 264.7 cell. Particularly, the purified GAG inhibited the proliferation of stomach cancer cell line, AGS, up to 40% for 72 hr incubation, but not the intestinal epithelial IEC-6 cell lines.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.3
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• pp.372-378
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• 2011

We extracted polysaccharide from the sea hare, Aplysia kurodai, purified it partially, and experimented its immune response using the human blood lymphocytes and macrophage cell lines. Aplysia kurodai polysaccharide fraction (APF) improved the growth of the T cell (Jurkat) up to 40% by treatment for 48 hours, and decreased the growth of blood cancer, Jiyoye cell line. The APF on RAW 264.7 cell also increased interleukin-12 up to 47%. In contrast, the secretion of interleukin-2 and interferon-gamma by treatment of only APF or APF and concanavalin A on Jurkat for 24 hours and 48 hours didn't influence significantly. These results suggest that the APF has possible immune regulating ability.

• Proceedings of the Zoological Society Korea Conference
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• 1999.10b
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• pp.189.1-189
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• 1999

No Abstract, See Full Text

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.11
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• pp.1647-1653
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• 2010

Glycosaminoglycan (GAG) was purified from polysaccharide extracted from sea hare muscle on DEAE-Sepharose column and investigated for the functional groups, distribution of sugars, composition of disaccharide and structure of GAG. Purified GAG was composed of disaccharide above 55% of total sugar. Purified GAG showed amide I peak in 1648/cm and C-O stretch peak as properties of carbohydrate, amino acid peak in 1457/cm, and peak in 866/cm as properties of monosaccharide by FT-IR. Fucose, N-acetylgalactosamine, N-acetylglucosamine, glucose, galactose, mannose and xylose were found in MALDI-TOF MS/MS spectra of hydrolysates by chondroitin sulfate ABC lyase and heparanase I. Purified GAG was expected to be heparan sulfate including N-acetylgalactosamine and N-acetylglucosamine above 70% of total sugar. The structure of GAG was supposed as GlyUA(2S)-GlcNS and GlyUA-GlcNS(6S) with O-linkage on protein core.

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.11
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• pp.1640-1646
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• 2010

The optimum condition was investigated for the extraction of glycosaminoglycan (GAG) from sea hare, Aplysia kurodai. The most effective enzyme was Flavourzyme for extraction of glycosaminoglycan. The optimum incubation temperature and time for hydrolysis were $60^{\circ}C$ and 15 hr, respectively. The yield of precipitated polysaccharide depended on Brix and ethanol volume. The most effective concentration of Brix and ethanol were sixty and 5 volume of ethanol, respectively. Most GAG was eluted between 0.5 M and 0.75 M NaCl gradient on DEAE-Sepharose column, and identified by electroconductivity. The contents of hexuronic acid from polysaccharide extract and GAG were 1.0 g/100 g and 6.0 g/100 g, respectively. Hexosamine of polysaccharide and GAG as indicator of GAG component was 5.6 g/100 g and 25.7 g/100 g, respectively. GAG was identified as heparan sulfate compared with bands of other GAG on agarose gel electrophoresis, and its molecular weight was 29.6 kDa on Superdex 200 HR column.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.3
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• pp.216-224
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• 1983

This work was undertaken to obtain some characteristics of proteolytic enzyme of marine gastropods such as sea hare, Aplysia kurodai, top shell, Turbo cornutus, and abalone, Haliotis discus hannai. An influence of pH, temperature and some chemicals on proteolytic activity of the crude enzyme extracted from digestive tract of the samples was taken into account and the stability of the enzyme during the storage at low temperature was also discussed. In comparison of the activities of the crude enzyme from the samples to the optimum conditions, it was characterized that abalone has twice or the more times higher activities than the other two species of the gastropoda in the acid and weak acid region, while, in the alkaline region, sea hare has six or the more times higher acitivities than the other two species. The proteolytic activity was facilitated by $Mn^{2+}$, some reducing agents, EDTA and DTT, and inhibited by $Hg^{2+}$ and SDS, but the other chemicals were not significantly affected to the activity. The low temperature storage of the enzymes of sea hare and top shell at $0^{\circ}C\;or\;-20^{\circ}C$ was not affected to the enzymic activity under the optimum pH condition except in the alkaline region. On the other hand, the low temperature storage was brought about no significant effect on the activity of the enzymes extracted from abalone under the optimum condition of the weak acid region, but apparently influenced to the activity under the optimum condition of the acid and alkaline region.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.279-284
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• 2001

This paper reports the purification of myomodulin A (MMA) and myomodulin E (MME) from the sea hare. The central nervous systems of 500 sea hare were extracted in an acidified solvent, after which four HPLC column systems were used to obtain pure peptides, The phasic contraction bioassay using a Mytilus edulis anterior byssus retractor muscle (ABRW) was applied to monitor all collected fractions. The pure peptides were submitted to Edman degradation based automated microsequencing. Mass spectrometry and chemical synthesis confirmed the sequence. The primary structures of MMA and MME were Pro-Met-Ser-Met-Leu-Arg-Leu-$NH_2$, (847.41 Da) and Cly-Leu-Gln-Met-Leu-Arg-Leu-$NH_2$, (830.50 Da), respectively. Synthetic peptides showed a modulating activity of phasic contraction in the ABRM of Mrtilus edulis.