Antimicrobial peptides derived from goose egg white lysozyme

Ovalbumin Hydrolysates Enhance Skeletal Muscle Insulin-Dependent Signaling Pathway in High-Fat Diet-Fed Mice

Egg white hydrolysates (EWH) and ovotransferrin-derived peptides have distinct beneficial effects on glucose metabolism. This research aims to investigate whether ovalbumin hydrolysates (OVAHs), without ovotransferrin can improve insulin signaling pathway in high-fat diet (HFD)-fed mice. Two types of ovalbumin hydrolysates were produced, either using thermoase (OVAT), or thermoase + pepsin (OVATP). Both OVAHs-supplemented groups exhibited lower body weight gain (P < 0.001) and enhanced oral glucose tolerance (P < 0.05) compared with HFD. Moreover, diet supplementation with either hydrolysate increased the insulin-stimulated activation of protein kinase B (AKT) and insulin receptor β (IRβ) (P < 0.0001) in skeletal muscle. In conclusion, OVAHs improved glucose tolerance and insulin-dependent signaling pathway in HFD-fed mice.

Expression of BSN314 lysozyme genes in Escherichia coli BL21: a study to demonstrate microbicidal and disintegarting potential of the cloned lysozyme

This study is an extension of our previous studies in which the lysozyme was isolated and purified from Bacillus subtilis BSN314 (Naveed et al., 2022; Naveed et al., 2023). In this study, the lysozyme genes were cloned into the E. coli BL21. For the expression of lysozyme in E. coli BL21, two target genes, Lyz-1 and Lyz-2, were ligated into the modified vector pET28a to generate pET28a-Lyz1 and pET28a-Lyz2, respectively. To increase the production rate of the enzyme, 0.5-mM concentration of IPTG was added to the culture media and incubated at 37 °C and 220 rpm for 24 h. Lyz1 was identified as N-acetylmuramoyl-L-alanine amidase and Lyz2 as D-alanyl-D-alanine carboxypeptidase. They were purified by multi-step methodology (ammonium sulfate, precipitation, dialysis, and ultrafiltration), and antimicrobial activity was determined. For Lyz1, the lowest MIC/MBC (0.25 μg/mL; with highest ZOI = 22 mm) were recorded against Micrococcus luteus, whereas the highest MIC/MBC with lowest ZOI were measured against Salmonella typhimurium (2.50 μg /mL; with ZOI = 10 mm). As compared with Aspergillus oryzae (MIC/MFC; 3.00 μg/mL), a higher concentration of lysozyme was required to control the growth of Saccharomyces cerevisiae (MIC/MFC; 50 μg/mL). Atomic force microscopy (AFM) was used to analyze the disintegrating effect of Lyz1 on the cells of selected Gram-positive bacteria, Gram-negative bacteria, and yeast. The AFM results showed that, as compared to Gram-negative bacteria, a lower concentration of lysozyme (Lyz1) was required to disintegrate the cell of Gram-positive bacteria.

Purification, Characterization and Bactericidal Action of Lysozyme, Isolated from Bacillus subtillis BSN314: A Disintegrating Effect of Lysozyme on Gram-Positive and Gram-Negative Bacteria

In the present study, lysozyme was purified by the following multi-step methodology: salt (ammonium sulfate) precipitation, dialysis, and ultrafiltration. The lysozyme potential was measured by enzymatic activity after each purification step. However, after ultrafiltration, the resulting material was considered extra purified. It was concentrated in an ultrafiltration centrifuge tube, and the resulting protein/lysozyme was used to determine its bactericidal potential against five bacterial strains, including three gram-positive (Bacillus subtilis 168, Micrococcus luteus, and Bacillus cereus) and two gram-negative (Salmonella typhimurium and Pseudomonas aeruginosa) strains. The results of ZOI and MIC/MBC showed that lysozyme had a higher antimicrobial activity against gram-positive than gram-negative bacterial strains. The results of the antibacterial activity of lysozyme were compared with those of ciprofloxacin (antibiotic). For this purpose, two indices were applied in the present study: antimicrobial index (AMI) and percent activity index (PAI). It was found that the purified lysozyme had a higher antibacterial activity against Bacillus cereus (AMI/PAI; 1.01/101) and Bacillus subtilis 168 (AMI/PAI; 1.03/103), compared to the antibiotic (ciprofloxacin) used in this study. Atomic force microscopy (AFM) was used to determine the bactericidal action of the lysozyme on the bacterial cell. The purified protein was further processed by gel column chromatography and the eluate was collected, its enzymatic activity was 21.93 U/mL, while the eluate was processed by native-PAGE. By this analysis, the un-denatured protein with enzymatic activity of 40.9 U/mL was obtained. This step shows that the protein (lysozyme) has an even higher enzymatic potential. To determine the specific peptides (in lysozyme) that may cause the bactericidal potential and cell lytic/enzymatic activity, the isolated protein (lysozyme) was further processed by the SDS-PAGE technique. SDS-PAGE analysis revealed different bands with sizes of 34 kDa, 24 kDa, and 10 kDa, respectively. To determine the chemical composition of the peptides, the bands (from SDS-PAGE) were cut, enzymatically digested, desalted, and analyzed by LC-MS (liquid chromatography-mass spectrometry). LC-MS analysis showed that the purified lysozyme had the following composition: the number of proteins in the sample was 56, the number of peptides was 124, and the number of PSMs (peptide spectrum matches) was 309. Among them, two peptides related to lysozyme and bactericidal activities were identified as: A0A1Q9G213 (N-acetylmuramoyl-L-alanine amidase) and A0A1Q9FRD3 (D-alanyl-D-alanine carboxypeptidase). The corresponding protein sequence and nucleic acid sequence were determined by comparison with the database.

Lysozyme and Its Application as Antibacterial Agent in Food Industry

Lysozymes are hydrolytic enzymes characterized by their ability to cleave the β-(1,4)-glycosidic bonds in peptidoglycan, a major structural component of the bacterial cell wall. This hydrolysis action compromises the integrity of the cell wall, causing the lysis of bacteria. For more than 80 years, its role of antibacterial defense in animals has been renowned, and it is also used as a preservative in foods and pharmaceuticals. In order to improve the antimicrobial efficacy of lysozyme, extensive research has been intended for its modifications. This manuscript reviews the natural antibiotic compound lysozyme with reference to its catalytic and non-catalytic mode of antibacterial action, lysozyme types, susceptibility and resistance of bacteria, modification of lysozyme molecules, and its applications in the food industry.

A g-Type Lysozyme from Deep-Sea Hydrothermal Vent Shrimp Kills Selectively Gram-Negative Bacteria

Lysozyme is a key effector molecule of the innate immune system in both vertebrate and invertebrate. It is classified into six types, one of which is the goose-type (g-type). To date, no study on g-type lysozyme in crustacean has been documented. Here, we report the identification and characterization of a g-type lysozyme (named LysG1) from the shrimp inhabiting a deep-sea hydrothermal vent in Manus Basin. LysG1 possesses conserved structural features of g-type lysozymes. The recombinant LysG1 (rLysG1) exhibited no muramidase activity and killed selectively Gram-negative bacteria in a manner that depended on temperature, pH, and metal ions. rLysG1 bound target bacteria via interaction with bacterial cell wall components, notably lipopolysaccharide (LPS), and induced cellular membrane permeabilization, which eventually caused cell lysis. The endotoxin-binding capacity enabled rLysG1 to alleviate the inflammatory response induced by LPS. Mutation analysis showed that the bacterial binding and killing activities of rLysG1 required the integrity of the conserved α3 and 4 helixes of the protein. Together, these results provide the first insight into the activity and working mechanism of g-type lysozyme in crustacean and deep-sea organisms.

Applications of Lysozyme, an Innate Immune Defense Factor, as an Alternative Antibiotic

Lysozyme is a ~14 kDa protein present in many mucosal secretions (tears, saliva, and mucus) and tissues of animals and plants, and plays an important role in the innate immunity, providing protection against bacteria, viruses, and fungi. Three main different types of lysozymes are known: the c-type (chicken or conventional type), the g-type (goose type), and the i-type (invertebrate type). It has long been the subject of several applications due to its antimicrobial properties. The problem of antibiotic resistance has stimulated the search for new molecules or new applications of known compounds. The use of lysozyme as an alternative antibiotic is the subject of this review, which covers the results published over the past two decades. This review is focused on the applications of lysozyme in medicine, (the treatment of infectious diseases, wound healing, and anti-biofilm), veterinary, feed, food preservation, and crop protection. It is available from a wide range of sources, in addition to the well-known chicken egg white, and its synergism with other compounds, endowed with antimicrobial activity, are also summarized. An overview of the modified lysozyme applications is provided in the form of tables.

Bioactivity of Hydrolysates Obtained from Chicken Egg Ovalbumin Using Artichoke (Cynara scolymus L.) Proteases

The aim of this work was to obtain chicken egg ovalbumin hydrolysates using aspartic proteinases present in extracts from the artichoke flower (Cynara scolymus L.) and evaluate their antioxidant, antimicrobial, and angiotensin I-converting enzyme (ACE) inhibitory activity in vitro. Hydrolysis time and molecular weight (<3 kDa) had a significant influence on the hypertensive and antioxidant activity of the hydrolysates. The <3 kDa fraction of the 16 h hydrolysate had an ACE inhibitory activity with an IC₅₀ of 64.06 µg peptides/mL. The fraction <3 kDa of ovalbumin hydrolysate at 2 h of hydrolysis showed a DPPH radical scavenging activity of 30.27 µM of Trolox equivalents/mg peptides. The fraction <3 kDa of the hydrolysate of 16 h had an ABTS⁺ caption activity of 4.30 mM of Trolox equivalents/mg peptides. The fraction <3 kDa of the hydrolysate of 2 h had an iron (II) chelating activity of 32.18 µg peptides/mL. From the peptide sequences identified in the hydrolysates, we detected four peptides (from the BIOPEP database) that were already in their bioactive form (IAAEVYEHTEGSTTSY, HLFGPPGKKDPV, PIAAEVYEHTEGSTTSY, and YAEERYPIL), and are reported to display antioxidant and ACE inhibitory activity.

A Novel Fluorescence Resonance Energy Transfer-Based High-Throughput Screening Method for Generation of Lysozyme with Improved Antimicrobial Activity against Escherichia coli Strains

Lysozyme has emerged to be a promising alternative to traditional antibiotics to deal with the increasing antibiotic resistance of bacteria. However, its application is hampered by its inferior bactericidal activity against Gram-negative bacteria. To address this problem, a novel "enzyme-cascade fluorescent high-throughput screening (HTS) method" was designed and constructed based on detection of fluorescence resonance energy transfer (FRET) and enzyme-cascade reaction of lysozyme and protease. As a proof of concept, site-saturation mutagenesis libraries targeting at residues of the unstructured stretch at the N-terminus of Antheraea pernyi lysozyme were constructed and screened by the proposed HTS method. The isolated lysozyme variants proved to exhibit higher antibacterial activity against Escherichia coli K12, demonstrating the significance of this region for the bactericidal function of lysozyme. The presented cell-based fluorescent HTS method is a new tool for screening lysozyme variants with improved bactericidal efficacy against Gram-negative bacteria and for exploring the sequence-structure-function relationship of lysozyme.

Effects of dietary lysozyme levels on growth performance, intestinal morphology, immunity response and microbiota community of growing pigs

BACKGROUND

Lysozyme has been studied as a potential alternative to antibiotics for animals in recent years. The aim of this study was to evaluate the effect of dietary lysozyme on growth performance, serum biochemical parameters, immune response and gut health of growing pigs.

RESULTS

A total of 216 growing pigs (19.81 ± 0.47 kg) were fed the diets supplemented with colistin sulfate at 20 mg kg^-1 (control), or lysozyme at 50 (L50) or 100 mg kg^-1 (L100) diet for 30 days. The results showed that pigs fed with L100 or control had greater average daily gain and gain-to-feed ratio than pigs in the L50 group. Pigs fed with L100 or colistin had greater villus height to crypt depth ratio in jejunum compared with pigs in the L50 group. Pigs fed with L100 had greater serum immunoglobulin A and jejunal secretory immunoglobulin A than control and L50, but lower serum total protein and globulin than control. No differences were observed in the messenger RNA expression of genes related to mucosal cytokines, antioxidant capacity, enzyme activity, and barrier functions among three treatments. The caecal microflora evenness was lower in the L100 group than in the control or L50 group by 16S ribosomal DNA sequencing. Phylogenetic investigation of communities by reconstruction of unobserved states analysis predicted that lysozyme may modify nutrient metabolism by changing intestinal microbial function of pigs.

CONCLUSIONS

Pigs supplemented with 100 mg kg^-1 lysozyme had similar growth performance and intestinal morphology as pigs fed with colistin. This was likely due to the improved systemic and gut immune responses and the reduced microbiota diversity by feeding 100 mg kg^-1 lysozyme. © 2018 Society of Chemical Industry.

Yeast Surface Display of Antheraea pernyi Lysozyme Revealed α-Helical Antibacterial Peptides in Its N-Terminal Domain

The present study investigated a novel lysozyme ApLyz from the Chinese oak silkmoth, Antheraea pernyi, for its active expression with N- or C-terminus fused to the yeast cell surface, and the antimicrobial activities of the corresponding expressed lysozymes were evaluated. The bactericidal activity of C-terminal fusion of ApLyz surpassed that of the N-terminal fusion, which revealed the implication of an N-terminal stretch of ApLyz in the bactericidal function based on the structural mobility of this region. Two N-terminal peptides of ApLyz (residues 1-15 and 1-32), which primarily consist of amphiphilic α-helices, exerted similar bactericidal efficacy and had a strong preference for the Gram-negative strains. Further investigation revealed that the N-terminal peptides are membrane-targeting peptides causing cell permeabilization and also possess nonmembrane disturbing bactericidal mechanism. Overall, in addition to the key findings of novel bactericidal peptides from silkmoth lysozyme, this work laid the foundation for future improvement of ApLyz by protein engineering.

Multiple specialised goose-type lysozymes potentially compensate for an exceptional lack of chicken-type lysozymes in Atlantic cod

Previous analyses of the Atlantic cod genome showed unique combinations of lacking and expanded number of genes for the immune system. The present study examined lysozyme activity, lysozyme gene distribution and expression in cod. Enzymatic assays employing specific bacterial lysozyme inhibitors provided evidence for presence of g-type, but unexpectedly not for c-type lysozyme activity. Database homology searches failed to identify any c-type lysozyme gene in the cod genome or in expressed sequence tags from cod. In contrast, we identified four g-type lysozyme genes (LygF1a-d) constitutively expressed, although differentially, in all cod organs examined. The active site glutamate residue is replaced by alanine in LygF1a, thus making it enzymatic inactive, while LygF1d was found in two active site variants carrying alanine or glutamate, respectively. In vitro and in vivo infection by the intracellular bacterium Francisella noatunensis gave a significantly reduced LygF1a and b expression but increased expression of the LygF1c and d genes as did also the interferon gamma (IFNγ) cytokine. These results demonstrate a lack of c-type lysozyme that is unprecedented among vertebrates. Our results further indicate that serial gene duplications have produced multiple differentially regulated cod g-type lysozymes with specialised functions potentially compensating for the lack of c-type lysozymes.

Application and bioactive properties of proteins and peptides derived from hen eggs: opportunities and challenges

Several proteins and peptides that are released in vitro and/or in vivo from hen eggs are biologically active and have a variety of functional properties in humans beyond normal nutrition, for which extensive studies have been performed. This review focuses on their biological activities, including antihypertensive, antioxidant, antimicrobial, antiadhesive, immunomodulatory and antithrombotic activities and enhancement of mineral absorption. These proteins and peptides have been shown to regulate the nervous system, cardiovascular system, immune system and gastrointestinal system. The potential application and future directions of research on these bioactive peptides and proteins in the food industry are also addressed.

Evolution of the vertebrate goose-type lysozyme gene family

BACKGROUND

Lysozyme g is an antibacterial enzyme that was first found in the eggs of some birds, but recently has been found in additional species, including non-vertebrates. Some previously characterized lysozyme g sequences are suggested to have altered secretion potential and enzymatic activity, however the distribution of these altered sequences is unknown. Duplicated copies of the lysozyme g gene exist in some species; however, the origins of the duplicates and their roles in altered function are unclear.

RESULTS

We identified 234 lysozyme g sequences from 118 vertebrate species, including 181 sequences that are full or near full length representing all vertebrate classes except cartilaginous fish. Phylogenetic analysis shows that most lysozyme g gene duplicates are recent or lineage specific events, however three amplification events are more ancient, those in an early amniote, an early mammal, and an early teleost. The older gene duplications are associated with changes in function, including changes in secretion potential and muramidase antibacterial enzymatic activity.

CONCLUSIONS

Lysozyme g is an essential muramidase enzyme that is widespread in vertebrates. Duplication of the lysozyme g gene, and the retention of non-secreted isozymes that have lost enzymatic activity indicate that lysozyme g has an activity other than the muramidase activity associated with being an antibacterial enzyme.

Secretory phospholipase A2 in dromedary tears: a host defense against staphylococci and other gram-positive bacteria

The best known physiologic function of secreted phospholipase A2 (sPLA2) group IIA (sPLA2-IIA) is defense against bacterial infection through hydrolytic degradation of bacterial membrane phospholipids. In fact, sPLA2-IIA effectively kills Gram-positive bacteria and to a lesser extent Gram-negative bacteria and is considered a major component of the eye's innate immune defense system. The antibacterial properties of sPLA2 have been demonstrated in rabbit and human tears. In this report, we have analyzed the bactericidal activity of dromedary tears and the subsequently purified sPLA2 on several Gram-positive bacteria. Our results showed that the sPLA2 displays a potent bactericidal activity against all the tested bacteria particularly against the Staphylococcus strains when tested in the ionic environment of tears. There is a synergic action of the sPLA2 with lysozyme when added to the bacteria culture prior to sPLA2. Interestingly, lysozyme purified from dromedary tears showed a significant bactericidal activity against Listeria monocytogene and Staphylococcus epidermidis, whereas the one purified from human tears displayed no activity against these two strains. We have also demonstrated that Ca(2+) is crucial for the activity of dromedary tear sPLA2 and to a less extent Mg(2+) ions. Given the presence of sPLA2 in tears and intestinal secretions, this enzyme may play a substantial role in innate mucosal and systemic bactericidal defenses against Gram-positive bacteria.

Preparation and evaluation of antioxidant activities of peptides obtained from defatted wheat germ by fermentation

Defatted wheat germ peptides (DWGPs) were prepared by fermentation with Bacillus Subtilis B1 and the antioxidant activities of DWGPs were investigated. The fermentation condition was optimized by response surface method (RSM) with three factors and three levels according to Box-Behnken theory. A maximal yield of DWGPs was achieved 8.69 mg/mL under optimal conditions: inoculum size 8%, fermentation temperature 31 °C and time 48 h. The main portion in the hydrolysates after fermentation was not free amino acid but peptide. The main molecular weight distribution of DWGPs was lower than 1000 Da. A positive correlation (R(2) = 0.9911) was found between concentration of DWGPs and total antioxidant capacity (T-AOC). DWGPs presented a significant does-dependent on scavenging activities of DPPH, hydroxyl and superoxide anion radicals. The EC50 values for the scavenging rates of DPPH, hydroxyl and superoxide anion radicals were 3.16 mg/mL, 6.04 mg/mL and 7.46 mg/mL, respectively. The results suggested that DWGPs produced by fermentation could be used as a promising antioxidant ingredient.

Antibacterial properties of chicken intestinal phospholipase A2

Background

The presence of chicken group-IIA PLA2 (ChPLA2-IIA) in the intestinal secretion suggests that this enzyme plays an important role in systemic bactericidal defence. We have analyzed the bactericidal activity of purified ChPLA2-IIA, on several gram-positive and gram-negative bacteria by using the diffusion well and dilution methods.

Results

ChPLA2-IIA displays potent bactericidal activity against gram-positive bacteria but lacks bactericidal activity against gram negative ones. We have also demonstrated a synergic action of ChPLA2-IIA with lysozyme when added to the bacteria culture prior to ChPLA2-IIA. The bactericidal efficiency of ChPLA2-IIA was shown to be dependent upon the presence of calcium ions and then a correlation could be made to its hydrolytic activity of membrane phospholipids. Interestingly ChPLA2-IIA displays a higher dependence to Ca2+ ions than to Mg2+ions.

Conclusion

We conclude that the main physiological role of ChPLA2-IIA could be the defence of the intestine against bacterial invasions.

Destabilase-lysozyme of medicinal leech. Multifunctionality of recombinant protein

Preparation and purification of a recombinant protein are described along with characteristics of its specific (for ε-(γ-Glu)-Lys and D-dimer substrates) and nonspecific (for L-γ-Glu-pNA) isopeptidase activities; the absence of peptidase function for α-(α-Glu)-Lys substrate is noted. It is shown that the protein exhibits muramidase (cell walls of Micrococcus lysodeikticus) and specific glycosidase activities. The latter was determined towards the fluorogenic substrate 4-methylumbelliferyl-tetra-N-acetyl-β-chitotetraoxide. Antimicrobial activity of recombinant destabilase-lysozyme protein (recDest-Lys) and its 11-membered amphipathic peptide was revealed towards cells of the strict anaerobic Archaean Methanosarcina barkeri, whose cell walls contain no murein. Possible mechanisms of the effect of recDest-Lys on these cells are discussed.