Determination of the Relationships between the Chemical Structure and Antimicrobial Activity of a GAPDH-Related Fish Antimicrobial Peptide and Analogs Thereof

Abstract

The structure–activity relationships and mode of action of synthesized glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-related antimicrobial peptides were investigated. Including the native skipjack tuna GAPDH-related peptide (SJGAP) of 32 amino acid residues (model for the study), 8 different peptide analogs were designed and synthesized to study the impact of net charge, hydrophobicity, amphipathicity, and secondary structure on both antibacterial and antifungal activities. A net positive charge increase, by the substitution of anionic residues or C-terminal amidation, improved the antimicrobial activity of the SJGAP analogs (minimal inhibitory concentrations of 16–64 μg/mL), whereas the alpha helix content, as determined by circular dichroism, did not have a very definite impact. The hydrophobicity of the peptides was also found to be important, especially for the improvement of antifungal activity. Membrane permeabilization assays showed that the active peptides induced significant cytoplasmic membrane permeabilization in the bacteria and yeast tested, but that this permeabilization did not cause leakage of 260 nm-absorbing intracellular material. This points to a mixed mode of action involving both membrane pore formation and targeting of intracellular components. This study is the first to highlight the links between the physicochemical properties, secondary structure, antimicrobial activity, and mechanism of action of antimicrobial peptides from scombrids or homologous to GAPDH.

Unlocking Antibacterial Potential: Key-Site-Based Regulation of Antibacterial Spectrum of Peptides

“…In this study, despite GG3A15 exhibiting the highest helicity, its overall antibacterial activity was slightly lower than that of GG3A7. This observation confirmed that augmenting the helicity of peptides with already favorable helical tendencies had limited on enhancing their activity. ,, More importantly, our investigation highlighted position 7 as a critical determinant of antibacterial activity in short α-helical peptides, which was consistent with analogous studies …”

Antibacterial Peptides derived from Capra hircus Goat Milk Casein

“…The hydrophobicity of peptides is also represented by the grand average of hydropathicity index (GRAVY) value, generated from Expassy – ProtParam tool (https://web.expasy.org/protparam/). The positive value of GRAVY shows that peptide is hydrophobic, while a negative value represents hydrophilic [25] . All peptides were categorized as hydrophilic, excluding P4 with a positive GRAVY value of 0.130.…”

“…The positive value of GRAVY shows that peptide is hydrophobic, while a negative value represents hydrophilic. [25] All peptides were categorized as hydrophilic, excluding P4 with a positive GRAVY value of 0.130.…”

Insights into Molecular Interactions between a GAPDH-Related Fish Antimicrobial Peptide, Analogs Thereof, and Bacterial Membranes

“…Interestingly, these three peptide analogs (5, 6, and 7) have demonstrated the ability to permeabilize the cytoplasmic membrane of the Gram-positive bacterium M. luteus, whereas analogs 1 and 8 did not exhibit significant permeabilization in tests involving the same microorganism …”

“…The results previously obtained in membrane permeabilization assays, together with the MICs and minimal bactericidal or fungicidal concentrations (MBCs and MFCs), pointed to a mixed mechanism of action in which both membrane permeabilization and intracellular targets seem involved. 42 Recent studies have assessed the antimicrobial activity of these analogs under various physicochemical conditions, quantifying their hemolytic activity, and investigating their digestibility in a dynamic model of human digestion. It was demonstrated that the antimicrobial activity of these peptides was stronger under acidic pH conditions and that it was sensitive to the presence of cations, in particular, divalent cations.…”