By reversing the amino acid sequence and attaching a cell-penetrating peptide, researchers doubled the antimicrobial power of a sea turtle defensin while significantly reducing its toxicity to human cells.
2× more potentReversing the peptide sequence and adding a cell-penetrating tag doubled antimicrobial activity against bacteria while reducing toxicity
What the researchers found
Researchers engineered three modified versions of TEWP, a defensin-like antimicrobial peptide originally found in sea turtle eggs. Reversing the peptide sequence and attaching a cell-penetrating peptide (CPP) doubled the antimicrobial activity while significantly reducing toxicity to human red blood cells. All variants were effective against 19 microbial strains, with the strongest activity against Listeria monocytogenes at concentrations of just 2–4 μg/mL.
The peptides were successfully produced at scale using engineered Pichia pastoris yeast and showed resistance to heat, protease degradation, and high salt concentrations — properties critical for real-world pharmaceutical use.
Why it matters
Antibiotic resistance is a growing global crisis, and antimicrobial peptides are one of the most promising alternatives to conventional antibiotics. This study tackles two key challenges: making these peptides more potent and less toxic through rational design, and producing them affordably at scale using yeast expression systems. The stability of these engineered peptides under harsh conditions makes them realistic candidates for pharmaceutical development.
The numbers in context
MIC: 2–4 μg/mL vs L. monocytogenes · 2-fold increase in antimicrobial activity (reversed + CPP variant) · Net charge +12 · 19 microbial strains tested · 96 h methanol induction · Produced in P. pastoris GS115
How the study worked
The researchers designed three TEWP analogs using different strategies: amino acid substitution (MTEWP), sequence reversal (RMTEWP), and conjugation with a cell-penetrating peptide ((RW)4RMTEWP). Each was produced recombinantly in Pichia pastoris yeast with a 6xHis tag. Antimicrobial activity was tested against 19 microbial strains, hemolytic activity was assessed, and stability was evaluated under heat treatment, protease exposure, and high salt conditions.
Who was studied
In vitro study testing engineered peptides against 19 microbial strains
What this study cannot tell us
This is an in vitro study only — no animal or human testing was performed. Activity against 19 lab strains may not reflect performance against clinical drug-resistant isolates. The production yields in Pichia pastoris were not quantified in the abstract. Long-term stability and in vivo pharmacokinetics remain unknown.
How to read the evidence
This is preliminary in vitro evidence demonstrating proof of concept for peptide engineering and production. While the antimicrobial data is clear and the production platform is robust, no animal or human testing has been performed.
When this study was published
Published in 2025, this is very recent work at the cutting edge of antimicrobial peptide engineering and recombinant production technology.
The bigger picture
As antibiotic resistance rises, the search for alternatives has turned to nature's antimicrobial peptides. This study demonstrates two key advances: rational peptide engineering can improve on nature's designs, and yeast-based production makes industrial manufacturing feasible. The combination of enhanced potency, reduced toxicity, and environmental stability addresses the main barriers that have prevented antimicrobial peptides from reaching the clinic.
Questions still open
- Would these engineered TEWP analogs remain effective against drug-resistant clinical isolates like MRSA or VRE?
- What happens to these peptides' antimicrobial activity when tested in animal infection models rather than lab cultures?
- Could the cell-penetrating peptide conjugation strategy be applied to other defensin family members to broadly improve antimicrobial peptides?
Common questions
Why study antimicrobial peptides from sea turtle eggs?
What is a cell-penetrating peptide and why attach one to an antibiotic?
Read the original research
Recombinant expression and functional characterization of defensin-like peptide TEWP and its analogs in Pichia pastoris.
World journal of microbiology & biotechnology, 41(10), 392
Citation
Batman, Saime Gülsüm; Kesmen, Zülal. (2025). Recombinant expression and functional characterization of defensin-like peptide TEWP and its analogs in Pichia pastoris.. World journal of microbiology & biotechnology, 41(10), 392. https://doi.org/10.1007/s11274-025-04618-x