An overview of antifungal peptides derived from insect

Fungi are not classified as plants or animals. They resemble plants in many ways but do not produce chlorophyll or make their own food photosynthetically like plants. Fungi are useful for the production of beer, bread, medicine, etc. More complex than viruses or bacteria; fungi can be destructive human pathogens responsible for various diseases in humans. Most people have a strong natural immunity against fungal infection. However, fungi can cause diseases when this immunity breaks down. In the last few years, fungal infection has increased strikingly and has been accompanied by a rise in the number of deaths of cancer patients, transplant recipients, and acquired immunodeficiency syndrome (AIDS) patients owing to fungal infections. The growth rate of fungi is very slow and quite difficult to identify. A series of molecules with antifungal activity against different strains of fungi have been found in insects, which can be of great importance to tackle human diseases. Insects secrete such compounds, which can be peptides, as a part of their immune defense reactions. Active antifungal peptides developed by insects to rapidly eliminate infectious pathogens are considered a component of the defense munitions. This review focuses on naturally occurring antifungal peptides from insects and their challenges to be used as armaments against human diseases.     

Amino acid conjugated sophorolipids: A new family of biologically active functionalized glycolipids

Sophorolipids (SLs) are extra cellular glycolipids produced by Candida bombicola ATCC 22214 when grown in the presence of glucose and fatty acids. These compounds have a disaccharide head group connected to a long-chain hydroxyl-fatty acid by a glycosidic bond. To explore structure-activity of modified SLs, a new family of amino acid-SL derivatives was prepared. Synthesized analogs consist of amino acids linked by amide bonds formed between their alpha-amino moiety and the carboxyl group of ring-opened SL fatty acids. Their preparation involved the following: (i) hydrolysis of a natural SL mixture with aqueous alkali to give SL free acids, (ii) coupling of free acids to protected amino acids using dicarbodiimide, and (iii) removing amino acid carboxyl protecting groups. These conjugates were evaluated for their antibacterial, anti-HIV, and spermicidal activity. All tested analogs showed antibacterial activity against both gram +ve and gram -ve organisms. Leucine-conjugated SL was most efficient. For example, the minimum inhibitory concentrations (MIC) for Moraxella sp. and E. coli were 0.83 and 1.67 mg/mL, respectively. Among the alkyl esters of amino acid conjugated SLs, the ethyl ester of leucine-SLs was most active. Against Moraxella sp., S. sanguinis, and M. imperiale, MIC values are 7.62 x 10(-4), 2.28 x 10-(3) and 1.67 mg/mL, respectively. All compounds displayed virus-inactivating activity with 50% effective concentrations (EC50) below 200 microg/mL. The EC50 of leucine-SL ethyl ester was 24.1 microg/mL, showing that it is more potent than commercial spermicide nonoxynol-9 (EC50 approximately 65 microg/mL).     

昆虫抗菌肽和抗真菌肽结构与功能的关系及分子设计

在对GenBank和EMBL数据库中登录的昆虫抗微生物肽 (antimicrobial peptide, AMP), 即昆虫抗菌肽 (antibacterial peptide) 和抗真菌肽 (antifungal peptide, AFP) 进行归类整理的基础上,对天蚕素族(cecropins )抗菌肽结构与功能的关系及人工改造的分子设计策略,特别是对目前新发现的一些昆虫抗真菌肽的已知结构与功能关系的研究进展、存在问题等进行了简要介绍和分析,为从事昆虫抗微生物肽的理论研究和发展新型抗生素药物提供了必要的信息。     

In-vitro antibacterial,antifungal and cytotoxic properties of metal-based furanyl derived sulfonamides

A new series of antibacterial and antifungal furanyl-derived sulfonamides and their cobalt (II), copper (II), nickel (II) and zinc (II) metal complexes have been synthesized, characterized and screened for their in-vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and, for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The results of these studies revealed that all compounds showed significant to moderate antibacterial activity. However, the zinc (II) complexes were found to be comparatively much more active as compared to the others. For antifungal activity generally, compounds (22) and (24) showed significant activity against Escherichia coli (a), (6) against Shigella flexeneri (b), (16) and (22) against Pseudomonas aeruginosa (c), (14) and (16) against Salmonella typhi (d), (9) against Staphylococcus aureus (e) and, (14) and (16) against Bacillus subtilis (f) fungal strains. The brine shrimp (Artemia salina) bioassay was also carried out to study their in-vitro cytotoxic properties. Only three compounds, (6), (10) and (23) displayed potent cytotoxic activity with LD₅₀ = 1.8535 × 10^{? 4}, 1.8173 × 10^{? 4} and 1.9291 × 10^{? 4} respectively.     

In-vitro antibacterial, antifungal and cytotoxic properties of metal-based furanyl derived sulfonamides

A new series of antibacterial and antifungal furanyl-derived sulfonamides and their cobalt (II), copper (II), nickel (II) and zinc (II) metal complexes have been synthesized, characterized and screened for their in-vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and, for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The results of these studies revealed that all compounds showed significant to moderate antibacterial activity. However, the zinc (II) complexes were found to be comparatively much more active as compared to the others. For antifungal activity generally, compounds (22) and (24) showed significant activity against Escherichia coli (a), (6) against Shigella flexeneri (b), (16) and (22) against Pseudomonas aeruginosa (c), (14) and (16) against Salmonella typhi (d), (9) against Staphylococcus aureus (e) and, (14) and (16) against Bacillus subtilis (f) fungal strains. The brine shrimp (Artemia salina) bioassay was also carried out to study their in-vitro cytotoxic properties. Only three compounds, (6), (10) and (23) displayed potent cytotoxic activity with LD50 = 1.8535 x 10(-4), 1.8173 x 10(-4) and 1.9291 x 10(-4) respectively.     

Characterization of blood group active glycopeptides derived from porcine kidneys

Sialoglycopeptide fractions were prepared from the pronase digest of porcine kidneys by DEAE-Sephadex A-25 column chromatography and gel-filtration through Sephadex G-100. Their chemical compositions and large molecular size suggested that these glycopeptides were derived from mucin-type glycoprotein(s). The results of the beta-elimination reaction indicated that they have the O-glycosidic linkages between N-acetylgalactosamine and serine/threonine. The glycopeptides exhibited blood group A and H activities. The present study revealed that the porcine kidney contains the blood group antigens of glycoprotein nature.     

Bestowing antifungal and antibacterial activities by lipophilic acid conjugation to D,L-amino acid-containing antimicrobial peptides: a plausible mode of action

The dramatically increased frequency of opportunistic fungal infections has prompted research to diversify the arsenal of antifungal agents. Antimicrobial peptides constitute a promising family for future antibiotics with a new mode of action. However, only a few are effective against fungal pathogens because of their ability to self-assemble. Recently, we showed that the conjugation of fatty acids to the potent antibacterial peptide magainin endowed it with antifungal activity concomitant with an increase in its oligomeric state in solution. To investigate whether a high potency of the parental peptide is prerequisite for antifungal activity, we conjugated undecanoic acid (UA) and palmitic acid (PA) to inactive diastereomers of magainin containing four d-amino acids ([D]-4-magainin), as well as to a weakly active diastereomeric lytic peptide containing Lys and Leu ([D]-K(5)L(7)). All lipopeptides gained potent activity toward Cryptococcus neoformans. Most importantly, [D]-K(5)L(7)-UA was highly potent against all microorganisms tested, including bacteria, yeast, and opportunistic fungi. All lipopeptides increased the permeability of Escherichia coli spheroplasts and intact C. neoformans, as well as their corresponding membranes, phosphatidylethanol (PE)/phosphatidylglycerol (PG) and phosphatidylcholine (PC)/PE/phosphatidylinositol (PI)/ergosterol, respectively. The extent of membrane-permeating activity correlated with their biological function, suggesting that the plasma membrane was one of their major targets. Circular dichroism (CD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy revealed that their mode of oligomerization in solution, structure, and organization in membranes have important roles regarding their antibacterial and antifungal activities. Together with the advantage of using diastereomers versus all l-amino acid peptides, this study paves the way to the design of a new group of potent antifungal peptides urgently needed to combat opportunistic fungal infection.     

Synthetic peptides derived from the beta2-beta3 loop of Raphanus sativus antifungal protein 2 that mimic the active site.

Rs-AFPs are antifungal proteins, isolated from radish (Raphanus sativus) seed or leaves, which consist of 50 or 51 amino acids and belong to the plant defensin family of proteins. Four highly homologous Rs-AFPs have been isolated (Rs-AFP1-4). The structure of Rs-AFP1 consists of three beta-strands and an alpha-helix, and is stabilized by four cystine bridges. Small peptides deduced from the native sequence, still having biological activity, are not only important tools to study structure-function relationships, but may also constitute a commercially interesting target. In an earlier study, we showed that the antifungal activity of Rs-AFP2 is concentrated mainly in the beta2-beta3 loop. In this study, we synthesized linear 19-mer peptides, spanning the entire beta2-beta3 loop, that were found to be almost as potent as Rs-AFP2. Cysteines, highly conserved in the native protein, are essential for maintaining the secondary structure of the protein. Surprisingly, in the 19-mer loop peptides, cysteines can be replaced by alpha-aminobutyric acid, which even improves the antifungal potency of the peptides. Analogous cyclic 19-mer peptides, forced to adopt a hairpin structure by the introduction of one or two non-native disulfide bridges, were also found to possess high antifungal activity. The synthetic 19-mer peptides, like Rs-AFP2 itself, cause increased Ca2+ influx in pregerminated fungal hyphae.     

Lipoxene: a new group of trihydroxy pentaenes of eicosapentaenoic acid derived from porcine leukocytes

Incubation of porcine leukocytes with [1-14C]-15-hydroperoxyeicosapentaenoic acid (15-HPEPE) results in the formation of a group of polar metabolites which after separation and purification by RP-HPLC and SP-HPLC were found to be a series of new compounds containing three hydroxy groups and four conjugated double bonds. The structures of these new metabolites were established by U. V. spectrophotometry and GC/MS to be trihydroxy pentaenes of EPA, i.e., 5,6,15-trihydroxy-7,9,11,13,17-eicosapentaenoic acid and 5,14,15-trihydroxy-6,8,10,12,17-eicosapentaenoic acid. Because of the additional double bond at C17-18, these two new metabolites of EPA were proposed to be lipoxene A and lipoxene B, respectively.     

海洋曲霉属真菌抗菌活性物质的研究进展

海洋微生物由于其独特的生存环境造就了许多结构新颖、具有特殊生物活性的代谢产物。随着科学技术的发展,科学界掀起了对海洋微生物代谢物的研究浪潮。近年来的研究表明,海洋曲霉属真菌及其次级代谢产物具有抗肿瘤、抗菌、抗病毒等生物活性。通过查阅文献与资料,对近年来海洋曲霉属真菌及其次级代谢产物的化学结构及生物活性研究与开发的进展进行综述总结,以期有助于后续研究及应用。     

Atriopeptins: a family of potent biologically active peptides derived from mammalian atria

Extracts of rat atria are potent stimulators of sodium and urine excretion, and relax vascular and intestinal smooth muscle preparations. The structures of six biologically active peptides obtained from atrial extracts are reported here. Ion exchange chromatography of a low molecular weight fraction obtained by gel filtration of atrial extracts produced two natriuretic fractions: the first induced relaxation of intestinal smooth muscle strips only, whereas the second also relaxed vascular strips as well. From the first fraction four pure biologically active peptides obtained by reverse phase HPLC have been sequenced: the 21 amino acid peptide, designated atriopeptin I, and three homologs (des- ser1 -, des- ser1 -ser2-, and des- ser21 - atriopeptin I). From the second fraction two pure biologically active peptides were obtained, which had C-terminal extensions of atriopeptin I: atriopeptins II (23 amino acid residues) and III (24 residues), having respectively phe-arg and phe-arg-tyr C-termini. These results suggest that this family of six peptides, sharing the same 17 membered ring formed by an internal cystine disulfide, is derived from a common high molecular weight precursor.     

Prediction of antiviral peptides derived from viral fusion proteins potentially active against herpes simplex and influenza A viruses

There are very few antiviral drugs available to fight viral infections and the appearance of viral strains resistant to these antiviralsis not a rare event. Hence, the design of new antiviral drugs is important. We describe the prediction of peptides with antiviralactivity (AVP) derived from the viral glycoproteins involved in the entrance of herpes simplex (HSV) and influenza A viruses intotheir host cells. It is known, that during this event viral glycoproteins suffer several conformational changes due to protein-proteininteractions, which lead to membrane fusion between the viral envelope and the cellular membrane. Our hypothesis is that AVPscan be derived from these viral glycoproteins, specifically from regions highly conserved in amino acid sequences, which at thesame time have the physicochemical properties of being highly exposed (antigenic), hydrophilic, flexible, and charged, since theseproperties are important for protein-protein interactions. For that, we separately analyzed the HSV glycoprotein H and B, andinfluenza A viruses hemagglutinin (HA), using several bioinformatics tools. A set of multiple alignments was carried out, to findthe most conserved regions in the amino acid sequences. Then, the physicochemical properties indicated above were analyzed. Wepredicted several peptides 12-20 amino acid length which by docking analysis were able to interact with the fusion viralglycoproteins and thus may prevent conformational changes in them, blocking the viral infection. Our strategy to design AVPsseems to be very promising since the peptides were synthetized and their antiviral activities have produced very encouragingresults.     

Isolation and sequence determination of trichorzianines A antifungal peptides from Trichoderma harzianum

Trichorzianines A, membrane active peptides of the peptaibol class, were isolated from cultures of the mould Trichoderma harzianum. Trichorzianines A were separated into pure components by HPLC on octadecyl bonded and SiO2 phases successively. Nine trichorzianines A (IIa, IIIa, IIIb, IIIc, IVb, Vb, VIa, VIb and VII) were isolated from the complex microheterogeneous mixture. Their N-terminal amino acid is acetylated, the C-terminal amino alcohol is either tryptophanol or phenylalaninol, 7 to 8 of the 19 residues are alpha-aminoisobutyric acid. Gas chromatography on a chiral phase showed isovaline to have the D-configuration and all the other optically active amino acids and amino alcohols to have the L-configuration. The amino acid sequences were determined from their positive ion FAB mass spectra which exhibited the preferential cleavage of the Aib 12-Pro 13 amide bond as a main fragmentation. The resulting fragments subsequently underwent amide bond ruptures that generated two series of abundant acylium ions which enabled direct determination of the 1-19 sequence. The relative position of the isomeric amino acids in the sequence of trichorzianine AVII was assigned from analysis of the N- and C-terminal oligopeptides yielded by its selective acidic hydrolysis. The microheterogeneity of trichorzianines A results mainly from single or multiple substitution of amino acids at the specific positions 5, 14, 16 and 19.     

A new capture test using conjugated peptides for the detection of HIV antibodies

Abstract A new capture test utilizing conjugated peptides has been developed for the detection of antibodies elicited against HIV-1. Human sera diluted 1:1000 were incubated in ELISA plates precoated with protein G. The captured IgG were allowed to react with three synthetic peptides corresponding to the gp41 sequence (591–611) YLKDQQLLGIWGCSGKLICTT, the gp120 sequence (314–329) IRIQRGPGRAFVTIGK and the p27 sequence (182–198) EWRFDSRLAFHHVAREL. The peptides were used in the form of N -hydroxysuccinimido-biotin ovalbumin conjugates. Peroxidase-labelled streptavidin was used to detect antigen-antibody complexes. The sensitivity and specificity of detection of antibodies were analyzed with 40 HIV positive sera, 10 seroconverting sera and 21 normal human sera (NHS). The results were compared with a commercial indirect ELISA in which a single conjugated gp41 peptide was used as antigenic probe. This indirect ELISA recognized 100% of the HIV positive and the seroconverting sera. The new capture test using the gp41 conjugated peptide also recognized 100% of the HIV positive sera but was more specific since it gave no false positive results whereas the indirect test did. The gp120 and p27 conjugated peptides detected 35/40 (87.5%) and 31/40 (77.5%) of HIV positive sera respectively and also detected 9/10 (90%) and 10/10 (100%) of the seroconverting sera respectively, without any false positive results (0/21). The proposed new capture test is a very sensitive and specific assay for detecting HIV antibodies.