Synthesis and PEGylation Strategy for Bradykinin-Potentiating Peptides from Animal Venoms

Polyethylene glycol (PEG) conjugation is one of the most established bioconjugation strategies and is FDA-approved due to its low toxicity, high solubility, extended circulation time, and low immunogenicity. In this study, we synthesized and PEGylated three venom-derived peptides: TsHpt-I17–25 (KETNAKPPA) from Tityus serrulatus scorpion venom, Lmr-BPP-9 (WPPRPQIPP) from Lachesis muta rhombeata snake venom, and Bj-BPP-10c (ENWPHPQIPP) from Bothrops jararaca snake venom, and evaluated their biological activities in vitro and in vivo. Peptides were obtained by solid-phase synthesis, purified by HPLC, and characterized by mass spectrometry and Tricine-SDS-PAGE. PEGylation was performed using mPEG-aldehyde, and ACE inhibitory activity in vitro was assessed for PEGylated and non-PEGylated forms. In vitro, Lmr-BPP-9 (IC50 = 5.19 ± 0.2 μg/1.56 ± 0.05 μM) and Bj-BPP-10c (IC50 = 13.59 ± 2.14 μg/4.08 ± 0.18 μM) showed significant ACE inhibition, whereas TsHpt-I17–25 was inactive. Notably, PEGylated peptides displayed no ACE inhibitory activity and were not tested in vivo. In vivo, the synthetic peptides Lmr-BPP-9 and Bj-BPP-10c did not reduce blood pressure, possibly due to proteolytic degradation or structural alterations during synthesis. Conversely, TsHpt-I17–25 unexpectedly induced a hypertensive response. In conclusion, our findings demonstrate both the therapeutic promise and the challenges of developing venom-derived peptides as drug leads. While PEGylation can enhance peptide stability, it may compromise biological activity, especially in small peptides. Future efforts should explore alternative conjugation strategies to preserve functionality while improving pharmacological properties.