Use this URL to cite or link to this record in EThOS:
Title: Peptidomic and genomic analyses on bioactive peptides from the amphibian skin
Author: Lv, Liangchun
ISNI:       0000 0004 7224 6245
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2017
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Thesis embargoed until 01 Aug 2023
Access from Institution:
Amphibian skin can secrete mucus from skin glands and this mucus always contains many types of antimicrobial peptides (AMPs) which can protect the hosts from bacterial infection. AMPs have been studied for a few decades with significant results as increasing numbers have been found, explored and developed to be evaluated as clinical drugs. This is a huge source of new molecules to help humans in their fight against diseases. In Chapter 3, a phylloxin-like AMP, QUB1966 and its analogue QUB2260, were studied. The results showed that QUB1966 exhibited antimicrobial effects against Gram-positive (Staphylococcus aureus) bacteria, Gram-negative (Escherichia coli) bacteria and yeast (Candida albicans). The modification increased the positive charge of the AMP, which enhanced the interaction between the peptide and the membrane of the selected microbes. The results showed that the modified peptide, QUB2260, expressed more potent antimicrobial function than the wild-type peptide QUB1966, increasing its inhibitory effect by 32-fold against E. coli and C. albicans, and 4-fold against S. aureus. Thus, the modified peptide might provide favourable prospects for novel biomedicine design and antibiotics substitution. In Chapter 4, a bradykinin-related peptide (BRP), QUB1315 (RAA-Val1, Thr6-bradykinin), was isolated from the skin secretion of Odorrana schmackeri with the defined primary sequence of RAAVPPGFTPFR. After bioactivity studies, QUB1351 revealed a dose-dependent contractile property on rat bladder. The analogue peptide, QUB1281 (RAA-Val1, Thr6, Leu8-bradykinin), was modified based on QUB1315 by replacing a single amino acid from Phe8 to Leu8 to test the antagonistic activity. However, the results showed that the modified peptide, QUB1281, was still an agonist. QUB1281 expressed less potency on bladder contraction than the wild-type QUB1315. It was also found that Thr6 and Leu8 might contribute to agonist effects and the substitution at position 8 could affect the affinity between peptides and bradykinin receptors. In Chapter 5, two novel peptides from Odorrana schmackeri, QUB1517 and QUB2025, were found to exhibit antibacterial potency against Gram-positive (Staphylococcus aureus) bacteria, Gram-negative (Escherichia coli) bacteria and yeast (Candida albicans). Their similar antimicrobial effects against these three microbes assumed that the same sequence domain might contribute to the antimicrobial activity. However, they both showed higher inhibitory activity on Gram-positive bacteria than Gram-negative bacteria. It is expected that the novel data described in this thesis will contribute to the burgeoning database of biologically-active peptides from amphibian skin secretions and may ultimately provide a basis for the development of new classes of peptide drugs for both major diseases and for orphan indications.
Supervisor: Zhou, Mei ; Chen, Tianbao ; Wang, Lei Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available