Microbial arginine deiminase: A multifaceted green catalyst in biomedical sciences

Enhanced thermostability and catalytic activity for arginine deiminase from Enterobacter faecalis SK32.001 via combinatorial mutagenesis

Arginine deiminase (ADI) exhibits potential for clinical and industrial applications, yet its low thermostability and catalytic efficiency under physiological conditions limit its utility. In this work, the ADI of Enterococcus faecalis SK32.001 was rationally designed. A total of 120 combinatorial mutants, ranging from two-point to six-point mutations, were constructed by sequentially stacking single-point positive mutants (F44W, N163P, E220L, N318E, A336G, T340I). Among them, the mutants S604, S700, S601, and S606 exhibited higher Tm values, while the mutants S605, S547, S602, S607, S517, and S557 demonstrated enhanced enzymatic activity. Notably, the five-point mutant S547 (F44W/N163P/E220I/A336G/T340I) exhibited remarkable pH tolerance (pH 4.5-9.5, with over 80 % residual enzyme activity). Its specific enzyme activity reached 131.60 U/mg, which was 2-fold higher than that of wild enzyme. The Tm value of this enzyme increases to 64.04 °C, 11.62 °C higher than that of the wild-type enzyme. The structure predicted by AlphaFold 2 revealed that the increased rigidity, formation of new hydrogen bonds, and an increase in hydrophobic residues may account for the enhanced enzyme activity and thermostability. This research demonstrates that rational design strategies can effectively optimize enzyme properties, providing insights for the development of microbial enzymes with industrial relevance.

Hybrid magnetic nanocomposites of arginine deiminase with improved stability and recyclability for biomedical applications

Nanocarrier-based immobilization has created new avenues for enhancing the biophysical properties of enzymes. Nanomatrices such as magnetite nanoparticles (MNPs), chitin, and chitosan with large surface areas and tunable morphology have been developed to circumvent the bottlenecks of free enzymes. The present study used MNPs to immobilize the enzyme arginine deiminase (ADI) for improved morphological control, recovery, operational stability, and easy recyclability. Hybrid magnetic arginine deiminase cross-linked enzyme aggregate (mADI-CLEA) was developed for the first time by co-aggregating ADI with magnetite nanocomposites, followed by its cross-linkage with glutaraldehyde. Structural analysis by DLS/ZETA, SEM, and FT-IR revealed their highly stable and robust nature. The resulting mADI-CLEA exhibited higher pH resistivity and thermostability than ADI-CLEA. Reusability and storage stability assay indicated that mADI-CLEA maintained more than 60% residual activity even after seven batch cycles and was stable for more than 70 days. These hybrid magnetic aggregates of ADI offer an economical and stable alternative for biomedical applications of ADI.

Nano- and Micro-Platforms in Therapeutic Proteins Delivery for Cancer Therapy: Materials and Strategies

Proteins have emerged as promising therapeutics in oncology due to their great specificity. Many treatment strategies are developed based on protein biologics, such as immunotherapy, starvation therapy, and pro-apoptosis therapy, while some protein biologics have entered the clinics. However, clinical translation is severely impeded by instability, short circulation time, poor transmembrane transportation, and immunogenicity. Micro- and nano-particles-based drug delivery platforms are designed to solve those problems and enhance protein therapeutic efficacy. This review first summarizes the different types of therapeutic proteins in clinical and research stages, highlighting their administration limitations. Next, various types of micro- and nano-particles are described to demonstrate how they can overcome those limitations. The potential of micro- and nano-particles are then explored to enhance the therapeutic efficacy of proteins by combinational therapies. Finally, the challenges and future directions of protein biologics carriers are discussed for optimized protein delivery.

Comprehensive insight into exploring the potential of microbial enzymes in cancer therapy: Progress, challenges, and opportunities: A review

Microbial enzymes are crucial catalysts in various industries due to their versatility and efficiency. The microbial enzymes market has recently expanded due to increased demand for many reasons. Among them are eco-friendly solutions, developing novel microbial strains with enhanced enzymes that perform under harsh conditions, providing sustainability, and raising awareness about the benefits of enzyme-based products. By 2030, the global enzyme market is expected to account for $525 billion, with a growth rate of 6.7 %. L-asparaginase and L-glutaminase are among the leading applied microbial enzymes in antitumor therapy, with a growing market share of 16.5 % and 9.5 %, respectively. The use of microbial enzymes has opened new opportunities to fight various tumors, including leukemia, lymphosarcoma, and breast cancer, which has increased their demand in the pharmaceutical and medicine sectors. Despite their promising applications, commercial use of microbial enzymes faces challenges such as short half-life, immunogenicity, toxicity, and other side effects. Therefore, this review explores the industrial production, purification, formulation, and commercial utilization of microbial enzymes, along with an overview of the global enzyme market. With ongoing discoveries of novel enzymes and their applications, enzyme technology offers promising avenues for cancer treatment and other therapeutic interventions.

Opportunities for nanomaterials in enzyme therapy

In recent years, enzyme therapy strategies have rapidly evolved to catalyze essential biochemical reactions with therapeutic potential. These approaches hold particular promise in addressing rare genetic disorders, cancer treatment, neurodegenerative conditions, wound healing, inflammation management, and infectious disease control, among others. There are several primary reasons for the utilization of enzymes as therapeutics: their substrate specificity, their biological compatibility, and their ability to generate a high number of product molecules per enzyme unit. These features have encouraged their application in enzyme replacement therapy where the enzyme serves as the therapeutic agent to rectify abnormal metabolic and physiological processes, enzyme prodrug therapy where the enzyme initiates a clinical effect by activating prodrugs, and enzyme dynamic or starving therapy where the enzyme acts upon host substrate molecules. Currently, there are >20 commercialized products based on therapeutic enzymes, but approval rates are considerably lower than other biologicals. This has stimulated nanobiotechnology in the last years to develop nanoparticle-based solutions that integrate therapeutic enzymes. This approach aims to enhance stability, prevent rapid clearance, reduce immunogenicity, and even enable spatio-temporal activation of the therapeutic catalyst. This comprehensive review delves into emerging trends in the application of therapeutic enzymes, with a particular emphasis on the synergistic opportunities presented by incorporating enzymes into nanomaterials. Such integration holds the promise of enhancing existing therapies or even paving the way for innovative nanotherapeutic approaches.

Recent trends in targeted delivery of smart nanocarrier-based microbial enzymes for therapeutic applications

Smart carrier-based immobilization has widened the use of enzymes for the treatment of several disorders. Large surface areas, tunable morphology, and surface modification ability aid the targeted and controlled release of therapeutic enzymes from such formulations. Smart nanocarriers, such as polymeric carriers, liposomes, and silica have also increased the stability, half-life, and permeability of these enzymes. In this review, summarize recent advances in the smart immobilization of microbial enzymes and their development as precision nanomedicine for the treatment of cancer, thrombosis, phenylketonuria (PKU), and wound healing. We also discuss the challenges and measures to be adopted for the successful clinical translation of these formulations.

Purification and characterization of L-arginine deiminase from Penicillium chrysogenum

L-arginine deiminase (ADI, EC 3.5.3.6) hydrolyzes arginine to ammonia and citrulline which is a natural supplement in health care. ADI was purified from Penicillium chrysogenum using 85% ammonium sulfate, DEAE-cellulose and Sephadex G200. ADI was purified 17.2-fold and 4.6% yield with a specific activity of 50 Umg- 1 protein. The molecular weight was 49 kDa. ADI expressed maximum activity at 40oC and an optimum pH of 6.0. ADI thermostability was investigated and the values of both t0.5 and D were determined. Kd increased by temperature and the Z value was 38oC. ATP, ADP and AMP activated ADI up to 0.6 mM. Cysteine and dithiothreitol activated ADI up to 60 µmol whereas the activation by thioglycolate and reduced glutathione (GSH) prolonged to 80 µmol. EDTA, α,α-dipyridyl, and o-phenanthroline inactivated ADI indicating that ADI is a metalloenzyme. N-ethylmaleimide (NEM), N-bromosuccinimide (NBS), butanedione (BD), dansyl chloride (DC), diethylpyrocarbonate (DEPC) and N-acetyl-imidazole (NAI) inhibited ADI activity indicating the necessity of sulfhydryl, tryptophanyl, arginyl, lysyl, histidyl and tyrosyl groups, respectively for ADI catalysis. The obtained results show that ADI from P. chrysogenum could be a potential candidate for industrial and biotechnological applications.

Streptococcal Arginine Deiminase Inhibits T Lymphocyte Differentiation In Vitro

Pathogenic microbes use arginine-metabolizing enzymes as an immune evasion strategy. In this study, the impact of streptococcal arginine deiminase (ADI) on the human peripheral blood T lymphocytes function in vitro was studied. The comparison of the effects of parental strain (Streptococcus pyogenes M49-16) with wild type of ArcA gene and its isogenic mutant with inactivated ArcA gene (Streptococcus pyogenes M49-16delArcA) was carried out. It was found that ADI in parental strain SDSC composition resulted in a fivefold decrease in the arginine concentration in human peripheral blood mononuclear cell (PBMC) supernatants. Only parental strain SDSCs suppressed anti-CD2/CD3/CD28-bead-stimulated mitochondrial dehydrogenase activity and caused a twofold decrease in IL-2 production in PBMC. Flow cytometry analysis revealed that ADI decreased the percentage of CM (central memory) and increased the proportion of TEMRA (terminally differentiated effector memory) of CD4+ and CD8+ T cells subsets. Enzyme activity inhibited the proliferation of all CD8+ T cell subsets as well as CM, EM (effector memory), and TEMRA CD4+ T cells. One of the prominent ADI effects was the inhibition of autophagy processes in CD8+ CM and EM as well as CD4+ CM, EM, and TEMRA T cell subsets. The data obtained confirm arginine's crucial role in controlling immune reactions and suggest that streptococcal ADI may downregulate adaptive immunity and immunological memory.

Amino Acids in Cancer and Cachexia: An Integrated View

Rapid tumor growth requires elevated biosynthetic activity, supported by metabolic rewiring occurring both intrinsically in cancer cells and extrinsically in the cancer host. The Warburg effect is one such example, burning glucose to produce a continuous flux of biomass substrates in cancer cells at the cost of energy wasting metabolic cycles in the host to maintain stable glycemia. Amino acid (AA) metabolism is profoundly altered in cancer cells, which use AAs for energy production and for supporting cell proliferation. The peculiarities in cancer AA metabolism allow the identification of specific vulnerabilities as targets of anti-cancer treatments. In the current review, specific approaches targeting AAs in terms of either deprivation or supplementation are discussed. Although based on opposed strategies, both show, in vitro and in vivo, positive effects. Any AA-targeted intervention will inevitably impact the cancer host, who frequently already has cachexia. Cancer cachexia is a wasting syndrome, also due to malnutrition, that compromises the effectiveness of anti-cancer drugs and eventually causes the patient's death. AA deprivation may exacerbate malnutrition and cachexia, while AA supplementation may improve the nutritional status, counteract cachexia, and predispose the patient to a more effective anti-cancer treatment. Here is provided an attempt to describe the AA-based therapeutic approaches that integrate currently distant points of view on cancer-centered and host-centered research, providing a glimpse of several potential investigations that approach cachexia as a unique cancer disease.

Enhancement of anti-tumor activity in melanoma using arginine deiminase fused with 30Kc19α protein

Arginine deiminase (ADI) is a microbial-derived enzyme which catalyzes the conversion of L-arginine into L-citrulline. ADI originating from Mycoplasma has been reported to present anti-tumor activity against arginine-auxotrophic tumors, including melanoma. Melanoma cells are sensitive to arginine depletion due to reduced expression of argininosuccinate synthase 1 (ASS1), a key enzyme for arginine biosynthesis. However, clinical applications of recombinant ADI for melanoma treatment present some limitations. Since recombinant ADI is not human-derived, it shows instability, proteolytic degradation, and antigenicity in human serum. In addition, there is a problem of drug resistance issue due to the intracellular expression of once-silenced ASS1. Moreover, recombinant ADI proteins are mainly expressed as inclusion body forms in Escherichia coli and require a time-consuming refolding process to turn them back into active form. Herein, we propose fusion of recombinant ADI from Mycoplasma hominis and 30Kc19α, a cell-penetrating protein which also increases stability and soluble expression of cargo proteins, to overcome these problems. We inserted matrix metalloproteinase-2 cleavable linker between ADI and 30Kc19α to increase enzyme activity in melanoma cells. Compared to ADI, ADI-LK-30Kc19α showed enhanced solubility, stability, and cell penetration. The fusion protein demonstrated selective cytotoxicity and reduced drug resistance in melanoma cells, thus would be a promising strategy for the improved efficacy in melanoma treatment. KEY POINTS: • Fusion of ADI with 30Kc19α enhances soluble expression and productivity of recombinant ADI in E. coli • 30Kc19α protects ADI from the proteolytic degradation by shielding effect, helping ADI to remain active • Intracellular delivery of ADI by 30Kc19α overcomes ADI resistance in melanoma cells by degrading intracellularly expressed arginine.

In silico and in vitro analysis of arginine deiminase from Pseudomonas furukawaii as a potential anticancer enzyme

Arginine deiminase (ADI), a promising anticancer enzyme from Mycoplasma hominis, is currently in phase III of clinical trials for the treatment of arginine auxotrophic tumors. However, it has been associated with several drawbacks in terms of low stability at human physiological conditions, high immunogenicity, hypersensitivity and systemic toxicity. In our previous work, Pseudomonas furukawaii 24 was identified as a potent producer of ADI with optimum activity under physiological conditions. In the present study, phylogenetic analysis of microbial ADIs indicated P. furukawaii ADI (PfADI) to be closely related to experimentally characterized ADIs of Pseudomonas sp. with proven anticancer activity. Immunoinformatics analysis was performed indicating lower immunogenicity of PfADI than MhADI (M. hominis ADI) both in terms of number of linear and conformational B-cell epitopes and T-cell epitope density. Overall antigenicity and allergenicity of PfADI was also lower as compared to MhADI, suggesting the applicability of PfADI as an alternative anticancer biotherapeutic. Hence, in vitro experiments were performed in which the ADI coding arcA gene of P. furukawaii was cloned and expressed in E. coli BL21. Recombinant ADI of P. furukawaii was purified, characterized and its anticancer activity was assessed. The enzyme was stable at human physiological conditions (pH 7 and 37 °C) with Km of 1.90 mM. PfADI was found to effectively inhibit the HepG2 cells with an IC50 value of 0.1950 IU/ml. Therefore, the current in silico and in vitro studies establish PfADI as a potential anticancer drug candidate with improved efficacy and low immunogenicity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03292-2.