Investigating the Mechanisms of the Biosynthesis of Lexapeptide

Antimicrobial resistance is one of the world’s greatest threats, as recognised by the World Health Organisation (WHO). Over the years, there has been an increase in the number of new resistance mechanisms which prevent or slow down the treatment of many common infections. This has led to the need for new antimicrobial agents to be discovered and developed for clinical use. One class of useful antimicrobials are the Lanthipeptides. Lanthipeptides are characterised by the presence of lanthionine macrocycles and α,β-unsaturated amino acids such as 2,3-dehydroalanine (Dha) and (Z)-2,3-dehydrobutyrine (Dhb). Currently, the only lanthipeptide that has been approved by the Food and Drugs Administration (FDA) is Nisin which has been used as a food preservative for over 40 years. This research focuses on lexapeptide. Lexapeptide is a class V lanthipeptide that was reported in 2020 and contains Dha and Dhb residues, a lanthionine ring, a D-alanine and a rare aminovinylmethyl cysteine (Avi(Me)Cys) ring at the C-terminus. These structural moieties give rise to potent activity against a wide range of Gram-positive bacteria, including methicillin resistant Staphylococcus aureus (MRSA) and allows for high stability against proteases, changes in pH and high temperatures. This excellent thermo- and pH-stability renders lexapeptide a potential candidate for antimicrobial drug development. However, the biosynthetic pathway that produces these structures are not fully understood, more specifically the pathway that leads to the formation of the Avi(Me)Cys moiety. In this thesis, the biosynthetic pathway and mechanisms for the addition of the Avi(Me)Cys moiety were investigated. The Avi(Me)Cys macrocycle is challenging to synthesise and the cause of many investigations into the total synthesis of Avi(Me)Cys-containing natural products to be discarded. By utilising the same biosynthetic enzymes used to incorporate this structure in nature, synthesised lexapeptide analogues can undergo the cyclisation in a chemo-enzymatic scheme to produce lexapeptide. The development of a chemo-enzymatic platform to enable the identification and employment of the correct native biosynthetic enzymes for Avi(Me)Cys formation is investigated herein. It is envisioned that this chemoenzymatic platform can then be used to synthesise lexapeptide and other Avi(Me)Cys containing analogues thereof.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Chemistry

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2025

Author dc:creator

• Grant-Mackie, Emily Susan

Advisors dc:contributor.advisor

• Brimble, Margaret
• Harris, Paul
• Bashiri, Ghader

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/74314

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/74314