The discovery of a novel peptide identified from the defensive skin secretion of Phyllomedusa hypochondrialis

Abstract

The process of searching for novel bioactive peptides in South American anurans was initially introduced in Phyllomedusa frogs. The poisonous skin secretions of this group of frogs are thought to have developed as a result of interactions between predators and prey as well as defense against microbial invasion. These complex mixtures of bioactive peptides are capable of warding off pathogens and prospective predators. New peptides with homologies to hormones, neurotransmitters, antibiotics, and a number of additional peptides with unclear biological activities are discovered for each newly discovered anuran species. It has been established that several substances have medicinal potential.In this thesis, a novel antimicrobial peptide, named QUB-2000, was isolated and identified in the secretions of the Phyllomedusa hypochondrialis. Via "shotgun" molecular cloning, the biosynthetic precursor sequence of QUB-2000 was obtained. Afterwards, RP-HPLC and MALDI-TOF-MS fragmentation sequencing was employed to double-confirm the primary structure of this novel peptide. The mature peptide was synthesised via solid phase peptide synthesis and subjected to minimal inhibitory concentration (MIC) assay using different micro-organisms and haemolytic activity assay using horse red blood cells. The results obtained from three individual experiments showed that QUB-2000 exhibited broad-spectrum antimicrobial abilities against S. aureus and E. coli with MIC values of 32 μM and 64 μM, respectively. QUB-2000 had weak antimicrobial activity against Candida albicans with MIC values of 128 μM. QUB-2000 exhibited no inhibitory effect against lung cancer cell line H838. Also, the haemolytic study of this novel peptide was found to be weak, with less than 5% haemolysis at 128 μM. Therefore, the peptide QUB-2000 has the potential to be an antimicrobial candidate.

Thesis is embargoed until 31 December 2029.

Date of Award	Dec 2024
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Chengbang Ma (Supervisor) & Lei Wang (Supervisor)