The Bioactivity Study of Mimetic Peptide Based on Rice Coleoptile Trypsin Inhibitor
| Autor: | Weng-long Lin, 林文龍 |
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| Rok vydání: | 2007 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 95 A 14 amino acid cyclic peptide with a disulfide bond protease inhibitor (SFTI) isolated from sunflower seeds showed a potential activity. It is thus interesting to explore the possibility for investigating small cyclic peptide having a disulfide bond as a potent protease inhibitor. We have isolated a protease inhibitor from rice coleoptiles with 133 amino acids, domain I of which has 33 amino acids. This peptide without the Cys7 was cyclized by a disulfide bond between Cys7 and Cys33, and was used as target for peptidomimetic study. It was found that the inhibitory activity in terms of Ki toward trypsin with L-BAPNA as substrate was 7.97 x 10-7 M and 9.50 x 10-7 M for disulfide bond cyclized peptide and non-cylized peptides, respectively.Both showed a competitive inhibitory behavior.The inhibitory constant (Ki) of this cyclo-target peptide was about twice of that for rice coleoptile protease inhibitor, Ki being 4.00 x 10-7 M and about 19 folds of that for SFTI, Ki being 5.00 x 10-8 M.Interestingly, it was found that the disulfide bond cyclized peptide and non-cyclized peptide showed a promising activity with Ki of 1.47 x 10-9 M and of 1.35 x 10-8, respectively, toward ��-chymotrypsin, which is competitive with the reported Ki value between 10-8 to 10-10 M,for various protease inhibitor toward ��-chymotrypsin, indicating this disulfide bond cyclized peptide showed a promising activity toward ��-chymotrypsin. Circular Dichroism spectroscopic studies showed that the content of ��-helix for cyclo- and noncyclo-peptide were 2.4% and 3.0%, respective; whileas, the content of ��-sheet were 46.8% and 54.4%, respectively. The disulfide bond was characterized by Circular Dichroism showing a signal at 202 nm and by IR spectroscopy showing a disulfide bond stretching finger print absorption between 470 to 700 cm-1. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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