PURIFICATION AND CHARACTERIZATION OF A NEW PEPTIDE (S-8300) FROM SHARK LIVER

S-8300, a small (8200.901 Da) antidiabetic peptide, was purified and characterized from shark livers (Chiloscyllium plagiosum). It was isolated by extraction of the water-soluble fraction, dialysis, ultrafiltration and dicthylaminoethyl Sepharose, Bio-Gel P-10 and fast protein liquid chromatography monoQ chromatography. The new peptide (S-8300) contained 17 amino acids and the 15 N-terminal amino acid residues of S-8300 were NH2-Met-Leu-Val-Gly-Pro-Ile-Gly-Ala-Ala-Lys-Val-Val-Tyr-Glu-Gln-. The new peptide was stable at 95C for 30 min and stable between pH 3.0 and 9.0. It was not inactivated by DNase and RNase, but totally inactivated by trypsin and proteinase K digestion. In addition, S-8300 could remarkably protect the structure integrity and recover the damage of NIT-1 cell after exposure to the toxin of streptozotocin. Homology search of NH2-terminal sequence showed that S-8300 was a totally new protein. PRACTICAL APPLICATIONS The experiments suggested that S-8300 could reduce the adverse effect of beta-cell toxins and protect the structure integrity and mitigate the damage. S-8300 could markedly decrease the level of fasting plasma glucose, glycohemoglobin-A1, triglyceride, cholesterol, free fatty acid and malondialdehyde, increased the activity of superoxide dismutase and attenuated the injury of beta-cell in pancreatic islet. Therefore, S-8300 has a significant protective effect on diabetes in mice. These might indicate that S-8300 could have clinical therapy significance.