| Lectin is a kind of sugar-specific protein or glycoprotein, it can prompt agglutination reaction of cells. Its history of study has more than 100 years. Lectin can combine with a large number of sugar-compound and form a series of biological functions. Lectin of animals and plants has a number of different functions. Lectin has a broad prospect of application because of its unique biological function. Researches on lectin more concentrated in higher plants early. Yeaton found lectin in 103 species of invertebrate, and inferred that all invertebrates have lectin in 2001. Lectin exist in serums of crustacean, mollusc and the other invertebrates, and it's often adsorbed on the membrane of blood cell.Apostichopus japonicus belongs to Echinodermata, Holothuroidea, Aspidochirota, Stichopodidae, Apostichopus. It usually inhabit in the shallow sea of north Pacific, Japan, Korea and Russia, and in china, it is mainly found in Liaoning, Hebei, Shandong and Jiangsu. Apostichopus japonicus is well know for its rich in Chondroitin sulfate, acidic mucopolysaccharides and collagen, and effect of enhancing human's immune system.Apostichopus japonicus live in marine with large numbers of bacteria, viruses and fungi and consume large numbers of organisms, bacteria and silt. It can survive healthily depended on its unique antibacterial mechanisms. Apostichopus japonicus is a kind of invertebrate which lack of adaptive immune, and its immune mechanism include its integument, coelomocyte, immune factors ( hemolysin and lectin ). The amount of lectin would be changed when external conditions impact Apostichopus japonicus.Since 1980s, rearing industry of Apostichopus japonicus is booming. At the same time, a series of diseases on rearing industry have emerged and bring enormous losses on rearing industry.Reared Apostichopus japonicus in China suffers from a kind of skin ulceration disease, which has caused severe economic loss in recent years. The course of this disease is often very short, usually several days. The infection involves a head shaking and viscera expelling at early time, and is followed with mouth and cloacal opening tumidity, then the body of the diseased individuals will be shrinking and titanic together with white or blue lesion spots on the body wall. In the later period, these small lesions grow more and bigger to large ulceration and finally causes the death of individuals. This disease is highly infectious, and can often cause all individuals reared in the same pool die in a very short time. And the pathogens are supposed to be bacterial by most researchers.Infecting Apostichopus japonicus by two kinds of pathogens of skin ulceration disease (Tenacibaculum and Vibrionales), isolating, purificating and identifying of their lectin. Detecting their hemagglutinating activity by erythrocyte, determining molecular weight, pH, heat resistance, etc.Lectin was purified from Apotichopus japonicus by extraction with PBS, followed by 20～75 % ammonium sulfate fractionation,ion exchange chromatography on the DEAE-Sepharose F.F. and molecular sieve chromatography on the Sephadex G-100. The subunit of lectin had a molecular weight of 31 000 Da on SDS-PAGE. The hemagglutinating activity for rabbit'erythrocyte could not be inhibited by D-fructose, D - mannose, D-glucose, D-galactose, L-rhamnose, sucrose, lactose, maltose, raffinose, but inhibited by bovine-thyroglobulin. Infected Apotichopus japonicus by tenacibaculum would produce much more lectin than the others, and its lectin is more prone to inhibited by bovine-thyroglobulin. The hemagglutinating activity was not inhibited by treatment with Ca2 + ,Mg2 + ,Mn2+,Zn2+ and EDTA. This lectin had the maximum hemagglutinating activity at pH 4. 5 - 7. 5, with activity at pH 4. 0 - 10. 14. The lectin still showed agglutinating activity after being treated with 90℃for 30 minutes , indicating that it had a high heat resistance. |
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