Isolation of probiotic lactobacilli strains harboring l-asparaginase and arginine deiminase genes from human infant feces for their potential application in cancer prevention

Recombinant Arginine Deiminase from Levilactobacillus brevis Inhibits the Growth of Stomach Cancer Cells, Possibly by Activating the Intrinsic Apoptosis Pathway

The anticancer potential of Levilactobacillus brevis KU15176 against the stomach cancer cell line AGS has been reported previously. In this study, we aimed to analyze the genome of L. brevis KU15176 and identify key genes that may have potential anticancer properties. Among potential anticancer molecules, the role of arginine deiminase (ADI) in conferring an antiproliferative functionality was confirmed. In vitro assay against AGS cell line confirmed that recombinant ADI from L. brevis KU15176 (ADI_br, 5 µg/mL), overexpressed in E. coli BL21 (DE3), exerted an inhibitory effect on AGS cell growth, resulting in a 65.32% reduction in cell viability. Moreover, the expression of apoptosis-related genes, such as bax, bad, caspase-7, and caspase-3, as well as the activity of caspase-9 in ADI_br-treated AGS cells, was higher than those in untreated (culture medium-only) cells. The cell-scattering behavior of ADI_br-treated cells showed characteristics of apoptosis. Flow cytometry analyses of AGS cells treated with ADI_br for 24 and 28 h revealed apoptotic rates of 11.87 and 24.09, respectively, indicating the progression of apoptosis in AGS cells after ADI_br treatment. This study highlights the potential of ADI_br as an effective enzyme for anticancer applications.

Metagenome-assembled genomes for biomarkers of bio-functionalities in Laal dahi, an Indian ethnic fermented milk product

Laal dahi is a sweetened and soft pudding-like fermented milk product of the Eastern regions of India, which has not been studied for its microbial community structures and health promoting functionality in terms of 'omics' approaches. We applied metagenomic and metagenomes-assembled genomes (MAGs) tools to decipher the biomarkers for genes encoding for different health promoting functionalities in laal dahi. Abundance of bacterial domains was observed with negligible presence of eukaryotes and viruses. Bacillota was the most abundant phylum with different bacterial species viz., Enterococcus italicus, Lactococcus raffinolactis, Lactobacillus helveticus, Bifidobacterium mongoliense, Hafnia alvei, Lactococcus lactis, Acetobacter okinawensis, Streptococcus thermophilus, Thermus thermophilus, Leuconostoc citreum, Leuconostoc pseudomesenteroides, Acetobacter orientalis, Lactobacillus gallinarum, Lactococcus chungangensis and Lactobacillus delbrueckii. Comparison of laal dahi microbiome with that of similar fermented milk products was also carried out after retrieving the metagenomic datasets from public databases. Significant abundance of Lb. helveticus, E. italicus, Lc. raffinolactis and Lc. lactis in laal dahi. Interestingly, Bifidobacterium mongoliense, Lb. gallinarum, Lc. chungangensis and Acetobacter okinawensis were only detected in laal dahi but Streptococcus infantarius, Lacticaseibacillus rhamnosus and Lb. johnsonii were absent. Reconstruction of putative single environment-specific genomes from metagenomes in addition to subsampling of the abundant species resulted in five high-quality MAGs identified as Lactobacillus delbrueckii, Lactobacillus helveticus, Lactococcus chungangensis, Lactococcus lactis and Streptococcus thermophilus. All MAGs showed the presence of various genes with several putative functions corresponding to different probiotic and prebiotic functions, short-chain fatty acids production, immunomodulation, antitumor genes, essential amino acid and vitamin biosynthesis. Genes for γ-Aminobutyric acid (GABA) production were only detected in MAG of Lactococcus lactis. Gene clusters for secondary metabolites (antimicrobial peptides) were detected in all MAGs except Lc. chungangensis. Additionally, detection of clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) elements was observed only in Lactobacillus delbrueckii and Streptococcus thermophilus. Annotation of several genes with potential health beneficial properties in all five MAGs may support the need to explore the culturability of these MAGs for future use in controlled fermentation of functional dairy products.

Arginine deiminase produced by lactic acid bacteria as a potent anti-cancer drug

Bacterial-based cancer immunotherapy has recently gained widespread attention due to its exceptional mechanism of rich pathogen-associated molecular patterns in anti-cancer immune responses. Contrary to conventional cancer therapies such as surgery, chemotherapy, radiation and phototherapy, bacteria-based cancer immunotherapy has the unique ability to suppress cancer by selectively accumulating and growing in tumours. In the view of this, several bacterial strains are being used for the treatment of cancer. Of which, lactic acid bacteria are a powerful, albeit still inadequately understood bacteria that possess a wide source of bioactive chemicals. Lactic acid bacteria metabolites, such as bacteriocins, short-chain fatty acids, exopolysaccharides show antitumour property. Amino acid pathways, which have lately been focussed as a new strategy to cancer therapy, are key element of the adaptability and dysregulation of metabolic pathways identified in proliferation of tumour cells. Arginine metabolism, in particular, has been shown to be critical for cancer therapy. As a result, better understanding of arginine metabolism in LAB and cancer cells could lead to new cancer therapeutic targets. This review will outline current advances in the interaction of arginine metabolism with cancer therapy and propose an arginine deiminase expression system to combat cancer more effectively.

Asparagine, colorectal cancer, and the role of sex, genes, microbes, and diet: A narrative review

Asparagine (Asn) and enzymes that catalyze the metabolism of Asn have been linked to the regulation and propagation of colorectal cancer (CRC). Increased Asn and asparagine synthetase (ASNS) expression, both contribute to CRC progression and metastasis. In contradistinction, L-asparaginase (ASNase) which breaks down Asn, exhibits an anti-tumor effect. Metabolic pathways such as KRAS/PI3K/AKT/mTORC1 signaling and high SOX12 expression can positively regulate endogenous Asn production. Conversely, the tumor suppressor, TP53, negatively impacts ASNS, thus limiting Asn synthesis and reducing tumor burden. Asn abundance can be altered by factors extrinsic to the cancer cell such as diet, the microbiome, and therapeutic use of ASNase. Recent studies have shown that sex-related factors can also influence the regulation of Asn, and high Asn production results in poorer prognosis for female CRC patients but not males. In this narrative review, we critically review studies that have examined endogenous and exogenous modulators of Asn bioavailability and summarize the key metabolic networks that regulate Asn metabolism. We also provide new hypotheses regarding sex-related influences on Asn, including the involvement of the sex-steroid hormone estrogen and estrogen receptors. Further, we hypothesize that sex-specific factors that influence Asn metabolism can influence clinical outcomes in CRC patients.

Acrylamide in Bakery Products: A Review on Health Risks, Legal Regulations and Strategies to Reduce Its Formation

Acrylamide is a contaminant as defined in Council Regulation (EEC) No 315/93 and as such, it is considered a chemical hazard in the food chain. The toxicity of acrylamide has been acknowledged since 2002, among its toxicological effects on humans being neurotoxicity, genotoxicity, carcinogenicity, and reproductive toxicity. Acrylamide has been classified as carcinogenic in the 2A group, with human exposure leading to progressive degeneration of the peripheral and central nervous systems characterized by cognitive and motor abnormalities. Bakery products (bread, crispbread, cakes, batter, breakfast cereals, biscuits, pies, etc.) are some of the major sources of dietary acrylamide. The review focuses on the levels of acrylamide in foods products, in particular bakery ones, and the risk that resulting dietary intake of acrylamide has on human health. The evolving legislative situation regarding the acrylamide content from foodstuffs, especially bakery ones, in the European Union is discussed underlining different measures that food producers must take in order to comply with the current regulations regarding the acrylamide levels in their products. Different approaches to reduce the acrylamide level in bakery products such as the use of asparginase, calcium salts, antioxidants, acids and their salts, etc., are described in detail.

The function and mechanism of lactic acid bacteria in the reduction of toxic substances in food: a review

N-nitrosamines, heterocyclic amines, polycyclic aromatic hydrocarbons, biogenic amines, and acrylamide are widely distributed and some of the most toxic substances detected in foods. Hence, reduction of these substances has attracted worldwide attention. Lactic acid bacteria (LAB) inoculation has been found to be an effective way to reduce these toxic substances. In this paper, the reduction of toxic substances by LAB and its underlying mechanisms have been described through the review of recent studies. LAB aids this reduction via different mechanisms. First, it can directly decrease these harmful substances through adsorption or degradation. Peptidoglycans on the cell wall of LAB can bind to heterocyclic amines, acrylamide, and polycyclic aromatic hydrocarbons. Second, LAB can indirectly decrease the content of toxic substances by reducing their precursors. Third, antioxidant properties of LAB also contribute to the reduction in toxic substances. Finally, LAB can suppress the growth of amino acid decarboxylase-positive bacteria, thus reducing the accumulation of biogenic amines and N-nitrosamines. Therefore, LAB can contribute to the decrease in toxic substances in food and improve food safety. Further research on increasing the reduction efficiency of LAB and deciphering the mechanisms at a molecular level needs to be carried out to obtain the complete picture.

Comparative proteomic analysis reveals metabolic variability of probiotic Enterococcus durans during aerobic and anaerobic cultivation

The variation in the bioavailability of oxygen constitutes the environmental conditions found by bacteria in their passage through the host gastro-intestinal tract. Given the importance of oxygen in the defense mechanism of bacteria, it is important to understand how bacteria respond to this stress at a metabolic level. The probiotic strain Enterococcus durans LAB18S was cultivated under aerobic and anaerobic conditions using prebiotic oligosaccharides as carbon source. The whole cell proteome and secretome were analyzed through label-free quantitative proteomics approach. The results showed that the LAB18S isolate when grown with fructo-oligosacchrides (FOS) showed a higher number of differentially expressed proteins compared to samples with galacto-oligosaccharides (GOS) or glucose. Clinically important enzymes for the treatment of cancer, L-asparaginase and arginine deiminase, were overexpressed when the isolate was cultured in FOS. In addition, the absence of oxygen induced the strain to produce proteins related to cell multiplication, cell wall integrity and resistance, and H₂O₂ detoxification. This study showed that E. durans LAB18S growing on FOS was stimulated to produce clinically important biomolecules, including proteins that have been investigated as potential antineoplastic agents. Significance: The probiotic strain E. durans LAB18S produce clinically relevant enzymes for the treatment of cancer when cultivated in symbiosis with fructo-oligosacchrides (FOS). In addition, proteins associated with cellular multiplication, cell wall integrity and resistance, and H₂O₂ detoxification were induced under anaerobic growth. These characteristics could be relevant to support maintenance of intestinal health.

Computational Analysis of Arginine Deiminase Sequences to Provide a Guideline for Protein Engineering

Background:

Arginine deiminase of Mycoplasma hominis, an arginine catabolizing enzyme, is currently in clinical trial for the treatment of arginine auxotrophic cancers. However, some drawbacks such as instability and antigenicity have limited its application as a protein drug. Arginine Deiminase (ADI) belongs to the guanidino-group modifying enzyme superfamily. Despite differences in the primary amino acid sequences of various members of this superfamily, the folding and secondary structures are conserved in all members. Despite structural similarities, ADIs in various species have different levels of catalytic activity and physicochemical properties due to the differences in their primary amino acid sequences. Therefore, investigating and comparing sequences between different ADI producing bacterial strains could be helpful in the rational engineering of ADI.

Objective:

In the current research, we used an in-silico approach to characterize and classify the available reviewed protein sequences of ADI.

Results:

102 ADI sequences from SwissProt database were extracted. Subsequently, based on clustering analyses, the sequence sets were divided into five distinct groups. Different physicochemical properties, solubility, and antigenicity of the enzymes were determined. Some ADI sequences were introduced as well-suited candidates for protein engineering; Lactobacillus fermentum ADI for low pI value, Mycobacterium avium ADI for high aliphatic index, Bacillus licheniformis ADI for low GRAVY index, Bradyrhizobium diazoefficiens ADI for low antigenicity and high stability index, and among Mycoplasma ADIs, Mycoplasma arthritidis ADI for high stability and aliphatic index, and Mycoplasma capricolum for low antigenicity.

Isolation and screening of extracellular anticancer enzymes from halophilic and halotolerant bacteria from different saline environments in Iran

It was confirmed that several enzymes have anti-cancer activity. The enzymes L-asparaginase, L-glutaminase, and L-arginase were chosen according to amino acids starvation in cancer cells and screened in halophilic and halotolerant bacteria, given probably less immunological reactions of halophilic or halotolerant enzymes in patients. Out of 110 halophilic and halotolerant strains, isolated from different saline environments in Iran and screened, some could produce a variety of anticancer enzymes. A total of 29, 4, and 2 strains produced L-asparaginase, L-glutaminase, and L-arginase, respectively. According to the phenotypic characteristics and partial 16S rRNA gene sequence analysis, the positive strains-strains with the ability to produce these anticancer enzymes-were identified as the members of the genera: Bacillus, Dietzia, Halobacillus, Rhodococcus, Paenibacillus and Planococcus as Gram-positive bacteria and Pseudomonas, Marinobacter, Halomonas, Idiomarina, Vibrio and Stappia as Gram-negative bacteria. The production of anticancer enzymes was mostly observed in the rod-shaped Gram-negative isolates, particularly in the members of the genera Halomonas and Marinobacter. Most of the enzymes were produced in the stationary phase of growth and the maximum enzyme activity was experienced in strain GBPx3 (Vibrio sp.) for L-asparaginase at 1.0 IU/ml, strain R₂S₂₅ (Rhodococcus sp.) for L-glutaminase at 0.6 IU/ml and strain GAAy3 (Planococcus sp.) for L-arginase at 3.1 IU/ml. The optimum temperature and pH for L-asparaginase and L-glutaminase activities in selected strains were similar to the physiological conditions of human body and the enzymes could tolerate NaCl up to 7.5% concentration.

Arginine Deiminase: Current Understanding and Applications

BACKGROUND

Arginine deiminase (ADI), an arginine catabolizing enzyme, is considered as an anti-tumor agent for the treatment of arginine auxotrophic cancers. However, some obstacles limit its clinical applications.

OBJECTIVE

This review will summarize the clinical applications of ADI, from a brief history to its limitations, and will discuss the different ways to deal with the clinical limitations.

METHOD

The structure analysis, cloning, expression, protein engineering and applications of arginine deiminase enzyme have been explained in this review.

CONCLUSION

Recent patents on ADI are related to ADI engineering to increase its efficacy for clinical application. The intracellular delivery of ADI and combination therapy seem to be the future strategies in the treatment of arginine auxotrophic cancers. Applying ADIs with optimum features from different sources and or ADI engineering, are promising strategies to improve the clinical application of ADI.

In silico analysis, molecular cloning, expression and characterization of l-asparaginase gene from Lactobacillus reuteri DSM 20016

l-Asparaginase is employed in leukaemic treatment and in processing starchy foods. The in silico analysis of Lactobacillus reuteri DSM 20016 reveals the presence of an l-asparaginase gene with theoretical pI value of 4.99. 3D structure prediction was carried out and one model was selected based on the validation scores of 86.293 for ERRAT, 92.10% for VERIFY 3D and Ramachandran plot. Multiple sequence alignment of the protein sequences of l-asparaginases I and II of Escherichia coli, Erwinia chrysanthemum and Homo sapiens shows their sequence similarity. The ORF LREU_RS09880 from L. reuteri DSM 20016 genome was cloned and expressed in E. coli. The recombinant protein was purified to homogeneity using Ni-NTA chromatography and showed higher substrate specificity for l-asparagine. Kinetic parameters like K_m and V_max of recombinant l-asparaginase were calculated as 0.3332 mM, 14.06 mM/min, respectively. Temperature and pH profile of recombinant l-asparaginase were analysed and maximum activity was found between 30 and 40 °C and at pH 6. The recombinant enzyme was thermally stable up to 24 h at 28 °C. Recombinant l-asparaginase has a recovery percentage of 92 and 10.5 fold purification. HPLC-MS-MS and SDS-PAGE analysis of the purified protein indicated a molecular weight of 35 kDa as a monomer.