Studies on the recombinant production and anticancer activity of thermostable L- asparaginase I from Pyrococcus abyssi

L-Asparaginase catalysing the breakdown of L-Asparagine to L-Aspartate and ammonia is an enzyme of therapeutic importance in the treatment of cancer, especially the lymphomas and leukaemia. The present study describes the recombinant production, properties and anticancer potential of enzyme from a hyperthermophilic archaeon Pyrococcus abyssi. There are two genes coding for asparaginase in the genome of this organism. A 918 bp gene encoding 305 amino acids was PCR amplified and cloned in BL21 (DE3) strain of E. coli using pET28a (+) plasmid. The production of recombinant enzyme was induced under 0.5mM IPTG, purified by selective heat denaturation and ion exchange chromatography. Purified enzyme was analyzed for kinetics, in silico structure and anticancer properties. The recombinant enzyme has shown a molecular weight of 33 kDa, specific activity of 1175 U/mg, KM value 2.05mM, optimum temperature and pH 80°C and 8 respectively. No detectable enzyme activity found when L-Glutamine was used as the substrate. In silico studies have shown that the enzyme exists as a homodimer having Arg11, Ala87, Thr110, His112, Gln142, Leu172, and Lys232 being the putative active site residues. The free energy change calculated by molecular docking studies of enzyme and substrate was found as ∆G – 4.5 kJ/mole indicating the affinity of enzyme with the substrate. IC50 values of 5U/mL to 7.5U/mL were determined for FB, caco2 cells and HepG2 cells. A calculated amount of enzyme (5U/mL) exhibited 78% to 55% growth inhibition of caco2 and HepG2 cells. In conclusion, the recombinant enzyme produced and characterized in the present study offers a good candidate for the treatment of cancer. The procedures adopted in the present study can be prolonged for in vivo studies.

Characterization of a Novel Thermostable Dye-Linked l-Lactate Dehydrogenase Complex and Its Application in Electrochemical Detection

Flavoenzyme dye-linked l-lactate dehydrogenase (Dye-LDH) is primarily involved in energy generation through electron transfer and exhibits potential utility in electrochemical devices. In this study, a gene encoding a Dye-LDH homolog was identified in a hyperthermophilic archaeon, Sulfurisphaera tokodaii. This gene was part of an operon that consisted of four genes that were tandemly arranged in the Sf. tokodaii genome in the following order: stk_16540, stk_16550 (dye-ldh homolog), stk_16560, and stk_16570. This gene cluster was expressed in an archaeal host, Sulfolobus acidocaldarius, and the produced enzyme was purified to homogeneity and characterized. The purified recombinant enzyme exhibited Dye-LDH activity and consisted of two different subunits (products of stk_16540 (α) and stk_16550 (β)), forming a heterohexameric structure (α3β3) with a molecular mass of approximately 253 kDa. Dye-LDH also exhibited excellent stability, retaining full activity upon incubation at 70 °C for 10 min and up to 80% activity after 30 min at 50 °C and pH 6.5–8.0. A quasi-direct electron transfer (DET)-type Dye-LDH was successfully developed by modification of the recombinant enzyme with an artificial redox mediator, phenazine ethosulfate, through amine groups on the enzyme’s surface. This study is the first report describing the development of a quasi-DET-type enzyme by using thermostable Dye-LDH.

Cloning, prokaryotic expression, and purification of acetyl-CoA C-acetyltransferase from Atractylodes lancea

Background: Cangzhu (Atractylodes lancea), a valuable and common traditional Chinese medicinal herb, is primarily used as an effective medicine with various health-promoting effects. The main pharmacological bioactive ingredients in the rhizome of A. lancea are terpenoids. Acetyl-CoA C-acetyltransferase (AACT) is the first enzyme in the terpenoid synthesis pathway and catalyzes two units of acetyl-CoA into acetoacetyl-CoA. Objective: The objective of the present work was to clone and identify function of AlAACT from Atractylodes lancea. Method: A full-length cDNA clone of AlAACT was isolated using PCR and expressed in Escherichia coli. The expressed protein was purified using Ni-NTA agarose column using standard protocols. AlAACT was transiently expressed in N. benthamiana leaves to determine their subcellular location. The difference in growth between recombinant bacteria and control bacteria under different stresses was observed using the droplet plate experiment. Result: In this study, a full-length cDNA of AACT (AlAACT) was cloned from A. lancea, which contains a 1,227 bp open reading frame and encodes a protein with 409 amino acids. Bioinformatic and phylogenetic analysis clearly suggested that AlAACT shared high similarity with AACTs from other plants. The recombinant protein pET32a(+)/AlAACT was successfully expressed in Escherichia coli BL21(DE3) cells induced with 0.4 mM IPTG at 30°C as the optimized condition. The recombinant enzyme pET-32a-AlAACT was purified using the Ni-NTA column based on the His-tag, and the molecular weight was determined to be 62 kDa through SDS-PAGE and Western Blot analysis. The recombinant protein was eluted with 100, 300, and 500 mM imidazole; most of the protein was eluted with 300 mM imidazole. Under mannitol stress, the recombinant pET-32a-AlAACT protein showed a substantial advantage in terms of growth rates compared to the control. However, this phenomenon was directly opposite under NaCl abiotic stress. Subcellular localization showed that AlAACT localizes to the nucleus and cytoplasm. Conclusion: The expression and purification of recombinant enzyme pET-32a-AlAACT were successful, and the recombinant strain pET-32a-AlAACT in showed better growth in a drought stress. The expression of AlAACT-EGFP fusion protein revealed its localization in both nuclear and cytoplasm compartments. This study provides an important foundation for further research into the effects of terpenoid biosynthesis in A. lancea.

Identification and Characterization of a Novel Carboxylesterase EstQ7 from a Soil Metagenomic Library

A novel lipolytic gene, estq7, was identified from a fosmid metagenomic library. The recombinant enzyme EstQ7 consists of 370 amino acids with an anticipated molecular mass of 42 kDa. Multiple sequence alignments showed that EstQ7 contained a pentapeptide motif GHSMG, and a putative catalytic triad Ser174–Asp306–His344. Interestingly, EstQ7 was found to have very little similarity to the characterized lipolytic enzymes. Phylogenetic analysis revealed that EstQ7 may be a member of a novel family of lipolytic enzymes. Biochemical characterization of the recombinant enzyme revealed that it constitutes a slightly alkalophilic, moderate thermophilic and highly active carboxylesterase against short chain fatty acid esters with optimum temperature 50 ℃ and pH 8.2. The Km and kcat values toward p-nitrophenyl acetate were determined to be 0.17 mM and 1910 S-1, respectively. Moreover, EstQ7 was demonstrated to have acyltransferase activity by GC-MS analysis. Homology modeling of the three-dimensional structure of this new enzyme showed that it exhibits a typical α/β hydrolase fold, and the catalytic triad residues are spatially close. Molecular docking reveled the interactions between the enzyme and the ligand. The high levels of lipolytic activity of EstQ7, combined with its moderate thermophilic property, and acyltransferase activity, render this novel enzyme a promising candidate biocatalyst for food, pharmaceutical and biotechnological applications.

Characterization of a GlgC homolog from extremely halophilic archaeon Haloarcula japonica

ABSTRACT Glycogen synthesis in bacteria is mainly organized by the products of glgB, glgC, and glgA genes comprising the widely known glg operon. On the genome of extremely halophilic archaeon Haloarcula japonica, there was a gene cluster analogous to the bacterial glg operon. In this study, we focused on a GlgC homolog of Ha. japonica, and its recombinant enzyme was prepared and characterized. The enzyme showed highest activity toward GTP and glucose-1-phosphate as substrates in the presence of 2.6 m KCl and predicted to be work as “GDP-glucose pyrophosphorylase” in Ha. japonica.

Optimization of Fermentation Conditions for Recombinant Lipase Expression At Small Scale Using Response Surface Methodology for Preliminary Production In Two Bioreactor Platforms.

Background: Pseudomonas lipases are widely used in industrial applications due to its unique biochemical properties, but one of the biggest limitations are the low yields obtained in native strains therefore, organisms as E. coli are used for the recombinant lipase overexpression. However, the recombinant lipase is accumulated as inclusion bodies and it affects biological activity, making that researchers evaluate different fermentation conditions to improve the activity of recombinant enzymes. In this study, a statistical experimental design was implemented to evaluate the effects of temperature, agitation rate and osmolyte concentration on the recombinant lipase activity produced in E. coli BL21 (DE3). Once the significant variables were identified, an optimization by a Response Surface Methodology was applied to maximize the lipase production. Results: The Box-Behnken designs revealed different optimal fermentation conditions for each osmolyte experiment. The glycerol showed the highest specific lipase activity compared to the other osmolytes and 0.1 M of osmolyte glycerol,5°C and 110 rpm showed the highest significant increase on the specific lipase activity and the data fitted the model very well. The validation showed that 452.01 U/mg of specific lipase activity was obtained which was significantly higher compared to the group where no glycerol was added (271.38 U/mg). The relative recombinant lipase expression was 2.7-fold lower at 5°C compared to 25 °C, but at 5°C the lipase activity was significantly higher. In addition, when the 3 L shaken Erlenmeyer Bioreactor was used to produce the recombinant lipase based on the power input parameter, the specific lipase activity was not significantly different from that found in Schott (408,4 U/mg and 452 U/mg, respectively), which means that this Bioreactor platform should be used for future scale-up processes.Conclusion: Low temperatures, low agitation rates and 0.1 M of glycerol in the autoinduction media enhanced the activity of the recombinant lipase produced in E. coli BL21(DE3). The optimized conditions and the 3 L shaken Erlenmeyer Bioreactor can be used to produce the recombinant enzyme in a higher volume based on the power input parameter. Further studies using this strategy may lead to the identification of optimal culture conditions for a given recombinant enzyme facilitating the large-scale bioprocess implementation.