Synthesis And Activity Of ACE-inhibitory Peptides

LGFPTTKTYFPHF and WYPWT were two hemoglobin fragments with high in vitroantihypertensive activity first isolated from enzyme hydrolysate of porcine hemoglobin. TheirIC50 values toward angiotensin I-converting enzyme were 4.92 and 6.02μM, respectively.In addition, the two peptides also showed low susceptibility to hydrolysis by gastrointestinalproteases and they both competitively inhibited ACE.Focused on the structure-activity relationship (SAR) among different peptides, weinvestigated the influence of amino acid composition and sequence changes of peptides onACE inhibitory activity. Here we synthesized 15 peptide analogues based on the structure ofLGFPTTKTYFPHF and VVYPWT and made research on the influence of C-and N-terminalamino acid on ACE inhibitory activity and make positive exploration of the use of peptidewith ACE inhibitory activity as anti_hypertensive drugs.We synthesized 17 peptides based on LGFPTTKTYFPHF and VVYPWT by solid phasepeptide synthesis method on Wang resin using Fmoc orthogonal protected strategy andHBTU-HOBt·H₂O as coupling reagents. After purification by gel filtration chromatographyand preparative reversed phase high performance liquid chromatography (RP-HPLC), thepeptides were identified by analytical RP-HPLC and ESI-MS.In vitro ACE inhibitory activity comparisons were made among 17 synthesized peptidesand these purified from porcine hemoglobin, among which LGFPTTKTYFPHF,GFPTTKTYFPHF, FPTTKTYFPHF, PTTKTYFPHF, TTKTYFPHF, TKYFPHF andVVYPWT showed relatively high activity similar with the naturally purified peptides. Theresults showed that peptides with high potent inhibitory activity have aromatic amino acid(Phe, etc) at the C-terminal and branched aliphatic amino acid at the N-terminal. And prolinewithin C-terminal tripepfides also showed influence on the activity. However, all thesynthesized peptides did not show obvious inhibition onα-glucosidase activity whichindicated that the peptides had no antihyperglycemic effect.The synthesis and bioactivity data indicated that peptides with high ACE inhibitoryactivity usually contain hydrophobic (aromatic, proline or branched-side chains) amino acid atthe C-terminal tripeptide and branched aliphatic amino acid at the N-terminal. Furtherinvestigation can be made on changes at the C-terminal amino acid and reduce hydrophilic amino acid under the premise of dissolution to obtain peptides with more potent ACEinhibitory activity.