Bioactive peptides from natural sources are currently favorable. Fruit seeds are sources of accumulated food, so there are potential sources for discovering bioactive peptides. In this research, an antioxidative peptides from longan seeds, named as Longan 1 (ISYVVPVYIAEITPKTFRGGF) was selected. However, direct extraction of the peptides from natural sources encounters some problems such as controlling of pepitide composition in protein hydrolysate. To overcome these problems, molecular genetic technique is chosen in this research by designing DNA fragment containing 4 repeats of the Longan 1 peptide linked by the codons of Aspartic acid in order to obtain adequetly long peptides for being manipulated by molecular genetic teqnique. Then, the DNA fragment wasinserted into the expression vector, pPICZαA and further integrated onto P. pastoris GS115 chromosome. After induction, the expected 10 and 20 kDa protein bands were revealed. However, they were not target peptide after being verified by mass spectrometry. Furthermore, there were several problems when using P. pastoris as expression host. Therefore, to solve these problems, the expression system was changed to Escherichia coli. The same DNA fragment was inserted into the plasmid pQE-30 Xa, and then transformed into E. coli MG1655. After induction, the expected 13 kDa protein band was found as in soluble protein fraction. It was found as recombinant target protein after being purified by affinity column and verified by Westrn blot. Moreover, the recombinant peptide was able to scavange free radicals, when characterized by several methods, especially nitric oxide when compared to the data of protein hydrolysate. The recombinant Longan 1 peptide was also revealed antiprolifative activity against stomach cancer, KATO-III.
