Influence of Dimerization of Lipopeptide Laur-Orn-Orn-Cys-NH2 and an N-terminal Peptide of Human Lactoferricin on Biological Activity

Enzymes as a Reservoir of Host Defence Peptides

Host defence peptides (HDPs) are powerful modulators of cellular responses to various types of insults caused by pathogen agents. To date, a wide range of HDPs, from species of different kingdoms including bacteria, plant and animal with extreme diversity in structure and biological activity, have been described. Apart from a limited number of peptides ribosomally synthesized, a large number of promising and multifunctional HDPs have been identified within protein precursors, with properties not necessarily related to innate immunity, consolidating the fascinating hypothesis that proteins have a second or even multiple biological mission in the form of one or more bio-active peptides. Among these precursors, enzymes constitute certainly an interesting group, because most of them are mainly globular and characterized by a fine specific internal structure closely related to their catalytic properties and also because they are yet little considered as potential HDP releasing proteins. In this regard, the main aim of the present review is to describe a panel of HDPs, identified in all canonical classes of enzymes, and to provide a detailed description on hydrolases and their corresponding HDPs, as there seems to exist a striking link between these structurally sophisticated catalysts and their high content in cationic and amphipathic cryptic peptides.

Anti-Inflammatory Effect of Homo- and Heterodimers of Natural Enkephalinase Inhibitors in Experimental Colitis in Mice

Background: the pharmacological treatment and/or maintenance of remission in inflammatory bowel diseases (IBDs) is currently one of the biggest challenges in the field of gastroenterology. Method: our aim was the synthesis of homo- and heterodimers of natural enkephalinase inhibitors (opiorphin; sialorphin; spinorphin) and the in vitro characterization of their effect on the degradation of enkephalin by neutral endopeptidase (NEP) and stability in human plasma. We investigated the in vivo heterodimer of Cys containing analogs of sialorphin and spinorphin (peptide X) in a mouse model of colitis. The extent of inflammation was evaluated based on the microscopic score; macroscopic score; ulcer score, colonic wall thickness, colon length and quantification of myeloperoxidase activity. Results: we showed that the homo- and heterodimerization of analogs of sialorphin, spinorphin and opiorphin containing Cys residue at the N-terminal position resulted in dimeric forms which in vitro exhibited higher inhibitory activity against NEP than their parent and monomeric forms. We showed that peptide X was more stable in human plasma than sialorphin and spinorphin. Peptide X exerts potent anti-inflammatory effect in the mouse model of colitis. Conclusion: we suggest that peptide X has the potential to become a valuable template for anti-inflammatory therapeutics for the treatment of gastrointestinal (GI) tract inflammation.

Advances in the Study of Structural Modification and Biological Activities of Anoplin

Anoplin is an amphipathic, α-helical bioactive peptide from wasp venom. In recent years, pharmaceutical and organic chemists discovered that anoplin and its derivatives showed multiple pharmacological activities in antibacterial, antitumor, antifungal, and antimalarial activities. Owing to the simple and unique structure and diverse biological activities, anoplin has attracted considerable research interests. This review highlights the advances in structural modification, biological activities, and the outlook of anoplin in order to provide a basis for new drug design and delivery.

Alanine Scanning Studies of the Antimicrobial Peptide Aurein 1.2

Antimicrobial peptides (AMPs) are compounds widely distributed in nature that display activity against a broad spectrum of pathogens. Amphibian skin, as an organ rich in pharmacologically active peptides, appears to be an interesting source of novel AMPs. Aurein 1.2 (GLFDIIKKIAESF-NH₂) is a short 13-residue antimicrobial peptide primarily isolated from the skin secretions of Australian bell frogs. In this study, the alanine scan of aurein 1.2 was performed to investigate the effect of each amino acid residue on its biological and physico-chemical properties. The biological studies included determination of minimum inhibitory concentration, activity against biofilm, and inhibitory effect on its formation. Moreover, the hemolytic activity as well as serum stability was determined. The hydrophobicity of peptides and their self-assembly were investigated using reversed-phase chromatography. In addition, their helicity was calculated from circular dichroism spectra. The results not only provided information on structure-activity relationship of aurein 1.2 but also gave insights into design of novel analogs of AMPs in the future.

Activity-Structure Study on the Peptide Fraction of AG2: a Potent In Vitro Transfection Agent

Gemini-based amphiphiles are candidates for biomedical applications. In fact, most of the gemini compounds described in the literature have been prepared to be used as new synthetic vectors in gene transfection. Our group carried out an activity-structure study starting from the structure of the gemini [AG2-C_18/]₂, which is an effective in vitro transfection reagent. We synthesized a series of novel amphiphilic amino acid derivatives of low molecular weight, named AGn-C_m (N), in which the same apolar region (m) of oleic or palmitic acid was maintained and the peptide region was modified by amino acid insertions, deletions, and substitutions. We also determined the transfection efficiency, critical micelle concentration, particle size, and ζ-potential for these derivatives. Amphiphiles AG10-C₁₆ and AG10-C₁₈ were more active at a lower N/P ratio than AG2-C₁₈. These amphiphiles showed no activity when lysine was replaced by ornithine, and the activity of all derivatives increased when there were more ornithine residues and a W/O = 1 ratio in the peptide region. It can be said that for AG10-C₁₆, these two structural requirements on the amino acid portion predominated over the type of aliphatic chain used.

Genomics-guided discovery and structure identification of cyclic lipopeptides from the Bacillus siamensis JFL15

In this research, a strain with broad-spectrum antimicrobial activities was isolated from the gastrointestinal tract of hairtail (Trichiurus haumela) and identified as Bacillus siamensis JFL15 through morphological, 16S rRNA, and average nucleotide identity analyses. The genome of B. siamensis JFL15 was sequenced, and three gene clusters involved in the biosynthesis of surfactin (srf), bacillibactin (dhb), and fengycin (fen) were predicted through antiSMASH analysis. The combined genomics-metabolics profiling of the strain revealed 20 active compounds, which belong to four main types of cyclic lipopeptides produced by Bacillus species: bacillibactin, iturin, fengycin, and surfactin. Among these lipopeptides, two high-purity antifungal components, namely, components b and c, were successfully identified as iturin A and bacillomycin F. The minimum inhibitory concentrations (MICs) of iturin A for Magnapothe grisea, Rhizoctorzia solani, and Colletotrichum gloeosporioides were 125.00, 62.50, and 125.00 μg/ml, respectively, whereas the MICs of bacillomycin F for these three organisms were 62.50, 31.25, and 62.50 μg/ml, respectively. The mechanism of bacillomycin F and iturin A against M. grisea was also investigated. Scanning electron microscopy (SEM) indicated that the surface of the hypha treated with iturin A or bacillomycin F became sunk, lumpy, and wrinkled. The diversity of the identified and predicted compounds from B. siamensis JFL15 suggested that this strain might be a promising biocontrol agent for an effective and environmentally friendly control of pathogenic microorganisms. To the best of our knowledge, this study is the first to describe cyclic lipopeptides purified and identified from B. siamensis.

Hydrocarbon Stapled Antimicrobial Peptides

Antimicrobial peptides are promising candidates for anti-infective pharmaceuticals. Unfortunately, because of their low proteolytic and chemical stability, their usage is generally narrowed down to topical formulations. Until now, numerous approaches to increase peptide stability have been proposed. One of them, peptide hydrocarbon stapling, a modification based on stabilizing peptide secondary structure with a side-chain covalent hydrocarbon bridge, have been successfully applied to many peptides. Moreover, constraining secondary structure of peptides have also been proven to increase their biological activity. This review article describes studies on hydrocarbon stapled antimicrobial peptides with respect to improved drug-like properties.

Recent advances in synthetic lipopeptides as anti-microbial agents: designs and synthetic approaches

Infectious diseases impose serious public health burdens and continue to be a global public health crisis. The treatment of infections caused by multidrug-resistant pathogens is challenging because only a few viable therapeutic options are clinically available. The emergence and risk of drug-resistant superbugs and the dearth of new classes of antibiotics have drawn increasing awareness that we may return to the pre-antibiotic era. To date, lipopeptides have been received considerable attention because of the following properties: They exhibit potent antimicrobial activities against a broad spectrum of pathogens, rapid bactericidal activity and have a different antimicrobial action compared with most of the conventional antibiotics used today and very slow development of drug resistance tendency. In general, lipopeptides can be structurally classified into two parts: a hydrophilic peptide moiety and a hydrophobic fatty acyl chain. To date, a significant amount of design and synthesis of lipopeptides have been done to improve the therapeutic potential of lipopeptides. This review will present the current knowledge and the recent research in design and synthesis of new lipopeptides and their derivatives in the last 5 years.