Rational surface engineering of an arginine deiminase (an antitumor enzyme) for increased PEGylation efficiency

Empowering Site-Specific Bioconjugations In Vitro and In Vivo: Advances in Sortase Engineering and Sortase-Mediated Ligation

Sortase-mediated ligation (SML) has emerged as a powerful and versatile methodology for site-specific protein conjugation, functionalization/labeling, immobilization, and design of biohybrid molecules and systems. However, the broader application of SML faces several challenges, such as limited activity and stability, dependence on calcium ions, and reversible reactions caused by nucleophilic side-products. Over the past decade, protein engineering campaigns and particularly directed evolution, have been extensively employed to overcome sortase limitations, thereby expanding the potential application of SML in multiple directions, including therapeutics, biorthogonal chemistry, biomaterials, and biosensors. This review provides an overview of achieved advancements in sortase engineering and highlights recent progress in utilizing SML in combination with other state-of-the-art chemical and biological methodologies. The aim is to encourage scientists to employ sortases in their conjugation experiments.

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.

Microbial arginine deiminase: A multifaceted green catalyst in biomedical sciences

Arginine deiminase is a well-recognized guanidino-modifying hydrolase that catalyzes the conversion of L-arginine to citrulline and ammonia. Their biopotential to regress tumors via amino acid deprivation therapy (AADT) has been well established. PEGylated formulation of recombinant Mycoplasma ADI is in the last-phase clinical trials against various arginine-auxotrophic cancers like hepatocellular carcinoma, melanoma, and mesothelioma. Recently, ADIs have attained immense importance in several other biomedical applications, namely treatment of Alzheimer's, as an antiviral drug, bioproduction of nutraceutical L-citrulline and bio-analytics involving L-arginine detection. Considering the wide applications of this biodrug, the demand for ADI is expected to escalate several-fold in the coming years. However, the sustainable production aspects of the enzyme with improved pharmacokinetics is still limited, creating bottlenecks for effective biopharmaceutical development. To circumvent the lacunae in enzyme production with appropriate paradigms of 'quality-by-design' an explicit overview of its properties with 'biobetter' formulations strategies are required. Present review provides an insight into all the potential biomedical applications of ADI along with the improvements required for its reach to clinics. Recent research advances with special emphasis on the development of ADI as a 'biobetter' enzyme have also been comprehensively elaborated.

Engineering of the Recombinant Expression and PEGylation Efficiency of the Therapeutic Enzyme Human Thymidine Phosphorylase

Human thymidine phosphorylase (HsTP) is an enzyme with important implications in the field of rare metabolic diseases. Defective mutations of HsTP lead to mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), a disease with a high unmet medical need that is associated with severe neurological and gastrointestinal complications. Current efforts focus on the development of an enzyme replacement therapy (ERT) using the Escherichia coli ortholog (EcTP). However, bacterial enzymes are counter-indicated for human therapeutic applications because they are recognized as foreign by the human immune system, thereby eliciting adverse immune responses and raising significant safety and efficacy risks. Thus, it is critical to utilize the HsTP enzyme as starting scaffold for pre-clinical drug development, thus de-risking the safety concerns associated with the use of bacterial enzymes. However, HsTP expresses very poorly in E. coli, whereas its PEGylation, a crucial chemical modification for achieving long serum persistence of therapeutic enzymes, is highly inefficient and negatively affects its catalytic activity. Here we focused on the engineering of the recombinant expression profile of HsTP in E. coli cells, as well as on the optimization of its PEGylation efficiency aiming at the development of an alternative therapeutic approach for MNGIE. We show that phylogenetic and structural analysis of proteins can provide important insights for the rational design of N’-terminus-truncation constructs which exhibit significantly improved recombinant expression levels. In addition, we developed and implemented a criteria-driven rational surface engineering strategy for the substitution of arginine-to-lysine and lysine-to-arginine residues to achieve more efficient, homogeneous and reproducible PEGylation without negatively affecting the enzymatic catalytic activity upon PEGylation. Collectively, our proposed strategies provide an effective way to optimize enzyme PEGylation and E. coli recombinant expression and are likely applicable for other proteins and enzymes.

Optimization of Nano-encapsulation on Neonatal Porcine Islet-like Cell Clusters Using Polymersomes

Researches proving methods for nano-encapsulation of neonatal porcine islet-like cell clusters (NPCCs) using polymersomes (PSomes) formed using polymers of polyethylene glycol-block-poly lactide. Herein, our studies present efficient nano-encapsulation procedure with minimal damage and loss of NPCCs.We used N-hydroxysuccinimide (NHS) on the N-terminal of PSomes to induce binding of amine groups in the extracellular matrix surrounding NPCCs. F-10 culture medium with bovine serum albumin was used in the nano-encapsulation procedure to minimize damage and loss of NPCCs. Finally, we induced cross-linking between bifunctional PSomes (NHS-/NH2-PSomes). F-10 culture medium containing 0.25% BSA with pH of 7.3 minimized the damage and loss of NPCCs after nano-encapsulation as compared with using basic HBSS buffer (pH 8.0). Also, we induced the efficient nano-encapsulation through conjugation of PSomes using bifunctional PSomes (NHS-/NH2-PSomes).

Simultaneous directed evolution of coupled enzymes for efficient asymmetric synthesis of l-phosphinothricin

The traditional strategy to improve the efficiency of an entire coupled enzyme system relies on separate direction of the evolution of enzymes involved in their respective enzymatic reactions. This strategy can lead to enhanced single-enzyme catalytic efficiency but may also lead to loss of coordination among enzymes. This study aimed to overcome such shortcomings by executing a directed evolution strategy on multiple enzymes in one combined group that catalyzes the asymmetric biosynthesis of l-phosphinothricin. The genes of a glutamate dehydrogenase from Pseudomonas moorei (PmGluDH) and a glucose dehydrogenase from Exiguobacterium sibiricum (EsGDH), along with other gene parts (promoters, ribosomal binding sites (RBSs), and terminators) were simultaneously evolved. The catalytic efficiency of PmGluDH was boosted by introducing the beneficial mutation A164G (from 1.29 s^-1mM^-1 to 183.52 s^-1mM^-1), and the EsGDH expression level was improved by optimizing the linker length between the RBS and the start codon of gdh. The total turnover numbers of the bioreaction increased from 115 (GluDH WT^NADPH) to 5846 (A164G^NADPH coupled with low expression of EsGDH), and to 33950 (A164G^NADPH coupled with high expression of EsGDH). The coupling efficiency was increased from ∼30% (GluDH_WT with low expression of GDH) to 83.3% (GluDH_A164G with high expression of GDH). In the batch production of l-phosphinothricin utilizing whole-cell catalysis, the strongest biocatalytic reaction exhibited a high space-time yield (6410 g·L^-1·d^-1) with strict stereoselectivity (>99% enantiomeric excess).Importance: The traditional strategy to improve multienzyme-catalyzed reaction efficiency may lead to enhanced single-enzyme catalytic efficiency but may also result in loss of coordination among enzymes. We describe a directed evolution strategy of an entire coupled enzyme system to simultaneously enhance enzyme coordination and catalytic efficiency. The simultaneous evolution strategy was applied to a multienzyme-catalyzed reaction for the asymmetric synthesis of l-phosphinothricin, which not only enhanced the catalytic efficiency of GluDH but also improved the coordination between GluDH and GDH. Since this strategy is enzyme-independent, it may be applicable to other coupled enzyme systems for chiral chemical synthesis.

Creation of a robust and R-selective ω-amine transaminase for the asymmetric synthesis of sitagliptin intermediate on a kilogram scale

The creation of an R-selective ω-amine transaminase (ω-ATA) as biocatalyst is crucial for the asymmetric amination of prochiral ketones to produce sitagliptin intermediates because rare ω-ATAs are R-selective in nature and most of them suffer from poor stability and low activity toward bulky prochiral ketones. Here, the gene of an R-selective ω-ATA was cloned from Arthrobacter cumminsii ZJUT212 (AcATA) and expressed in Escherichia coli. The best variants (M1 + M122H and M1+T134 G) were obtained using a semi-rational protein design after screening. These variants not only exhibited improved activity and substrate affinity but also enhanced stability in aqueous phase containing 20 % dimethyl sulfoxide. The conversion of asymmetric amination on 50 g/L pro-sitagliptin ketone PTfpB (1-[1-piperidinyl]-4-[2,4,5-trifluorophenyl]-1,3-butanedione) achieved 92 %, with an extremely high e.e. of >99 %, using 2 g_DCW/L E. coli cells harboring M1 + M122H as biocatalyst. In the kilogram-scale experiment, approximately 40 kg of (R)-APTfpB (e.e. >99 %) was produced within 30 h when 50 kg PTfpB was used as the substrate. Furthermore, the space-time yield reached ≈32 g/(L·d).