Angiotensin converting enzyme inhibitory activity of kefir and expression of recombinant angiotensin converting enzyme inhibitory peptide in Escherichia coli

• Main Authors: Yen-Po Chen, 陳彥伯
• Other Authors: Chin-Wen Lin
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/31159806636277880080

碩士 === 國立臺灣大學 === 畜產學研究所 === 92 === Angiotensin converting enzyme (ACE) is a key enzyme on blood pressure regulation. Inhibition of ACE can be used for antihypertensive therapy, and many clinical antihypertensive drugs have been designed as ACE inhibitor. One purpose of this study is to investigate the ACE inhibitory activity of kefir during different storage and ripening periods. Another object is to produce precursor type recombinant ACE inhibitory peptide in Escherichia coli. Experiment I was conducted to assay ACE inhibitory activity of alcoholic fermented milk, kefir, in different media and conditions. Kefir was fermented by inoculating kefir grains (starter) in bovine and capric milk. We investigated the optimal storage and ripening time for fermenting kefir exhibiting the maximum ACE inhibitory activity. The results showed that ACE inhibitory activity was weak in both bovine and capric kefir during fermentation. However, when kefir were stored at 4℃ for 1 to 7 days, ACE inhibitory activity was improved. When ripened with kefir grains at 4℃ and then stored for various periods, the ACE inhibitory activity was more strong. The capric kefir with 3-day ripening and 3-day storage reached the maximum ACE inhibitory activity. These results suggested kefir exhibited antihypertensive activity in vitro. Further study will focus on the purification of the ACE inhibitory substances and the antihypertensive activity of kefir in animal model. Experiment II produced prodrug type recombinant ACE inhibitory peptide in E. coli. We used synthesized complementary oligonucleotide annealed to make artificial ACE inhibitory peptide gene monomer which can translate to two copies of ACE inhibitory peptide of Phe-Phe-Val-Ala-Pro. In order to produce prodrug type recombinant protein carried many copies of ACE inhibitory peptide, we ligated each monomer of ACE inhibitory peptide gene. The multimer gene was ligated with pQE31 vector and transformed to E. coli strain DH5? Polymerase chain reaction (PCR) was used to screen the correct transformant and to determine the copy number of inserted gene. PCR positive strains were then confirmed by DNA sequencing. We have collected two strains that harbored ACE inhibitory peptide gene for completely two and three copies of Phe-Phe-Val-Ala-Pro peptide translation. The further works will analyze recombinant peptide expression and biological function.