Purification, characterization and kinetic properties of the Taenia solium glutathione S -transferase isoform 26.5�kDa

Stress-Based Production, and Characterization of Glutathione Peroxidase and Glutathione S-Transferase Enzymes From Lactobacillus plantarum

More attention has been recently directed toward glutathione peroxidase and s-transferase enzymes because of the great importance they hold with respect to their applications in the pharmaceutical field. This work was conducted to optimize the production and characterize glutathione peroxidase and glutathione s-transferase produced by Lactobacillus plantarum KU720558 using Plackett-Burman and Box-Behnken statistical designs. To assess the impact of the culture conditions on the microbial production of the enzymes, colorimetric methods were used. Following data analysis, the optimum conditions that enhanced the s-transferase yield were the De Man-Rogosa-Sharp (MRS) broth as a basal medium supplemented with 0.1% urea, 0.075% H₂O₂, 0.5% 1-butanol, 0.0125% amino acids, and 0.05% SDS at pH 6.0 and anaerobically incubated for 24 h at 40°C. The optimum s-transferase specific activity was 1789.5 U/mg of protein, which was ~12 times the activity of the basal medium. For peroxidase, the best medium composition was 0.17% urea, 0.025% bile salt, 7.5% Na Cl, 0.05% H₂O₂, 0.05% SDS, and 2% ethanol added to the MRS broth at pH 6.0 and anaerobically incubated for 24 h at 40°C. Furthermore, the optimum peroxidase specific activity was 612.5 U/mg of protein, indicating that its activity was 22 times higher than the activity recorded in the basal medium. After SDS-PAGE analysis, GST and GPx showed a single protein band of 25 and 18 kDa, respectively. They were able to retain their activities at an optimal temperature of 40°C for an hour and pH range 4–7. The 3D model of both enzymes was constructed showing helical structures, sheet and loops. Protein cavities were also detected to define druggable sites. GST model had two large pockets; 185Å3 and 71 Å3 with druggability score 0.5–0.8. For GPx, the pockets were relatively smaller, 71 Å3 and 32 Å3 with druggability score (0.65–0.66). Therefore, the present study showed that the consortium components as well as the stress-based conditions used could express both enzymes with enhanced productivity, recommending their application based on the obtained results.

Partial purification and characterization of glutathione S-transferase from the somatic tissue of Gastrothylax crumenifer (Trematoda: Digenea)

AIM

Aim of the present study was to carry out the partial purification and biochemical characterization of glutathione S-transferase (GST) from the somatic tissue of ruminal amphistome parasite, Gastrothylax crumenifer (Gc) infecting Indian water buffalo (Bubalus bubalis).

MATERIALS AND METHODS

The crude somatic homogenate of Gc was subjected to progressive ammonium sulfate precipitation followed by size exclusion chromatography in a Sephacryl S 100-HR column. The partially purified GST was assayed spectrophotometrically, and the corresponding enzyme activity was also recorded in polyacrylamide gel. GST isolated from the amphistome parasite was also exposed to variable changes in temperature and the pH gradient of the assay mixture.

RESULTS

The precipitated amphistome GST molecules showed maximum activity in the sixth elution fraction. The GST subunit appeared as a single band in the reducing polyacrylamide gel electrophoresis with an apparent molecular weight of 26 kDa. The GST proteins were found to be fairly stable up to 37°C, beyond this the activity got heavily impaired. Further, the GST obtained showed a pH optima of 7.5.

CONCLUSION

Present findings showed that GST from Gc could be conveniently purified using gel filtration chromatography. The purified enzyme showed maximum stability and activity at 4°C.

Two glutathione transferase isoforms isolated from juvenile cysts of Taenia crassiceps: identification, purification and characterization

We identified and characterized the first two glutathione transferases (GSTs) isolated from juvenile cysts of Taenia crassiceps (EC 2.5.1.18). The two glutathione transferases (TcGST1 and TcGST2) were purified in a single-step protocol using glutathione (GSH)-sepharose chromatography in combination with a GSH gradient. The specific activities of TcGST1 and TcGST2 were 26 U mg-1 and 19 U mg-1, respectively, both at 25°C and pH 6.5 with 1-chloro-2,4-dinitrobenzene (CDNB) and GSH as substrates. The Km(CDNB) and Kcat(CDNB) values for TcGST1 and TcGST2 (0.86 μm and 62 s-1; 1.03 μm and 1.97 s-1, respectively) and Km(GSH) and Kcat(GSH) values for TcGST1 and TcGST2 (0.55 μm and 11.61 s-1; 0.3 μm and 32.3 s-1, respectively) were similar to those reported for mammalian and helminth GSTs. Mass spectrometry analysis showed that eight peptides from each of the two parasite transferases were a match for gi|29825896 glutathione transferase (Taenia solium), confirming that both enzymes are GSTs. The relative molecular masses were 54,000 ± 0.9 for the native enzymes and 27,500 ± 0.5 for the enzyme subunits. Thus, TcGST1 and TcGST2 are dimeric proteins. Optimal TcGST1 and TcGST2 activities were observed at pH 8.5 in the range of 20-55°C and pH 7.5 at 35-40°C, respectively. TcGST1 and TcGST2 were inhibited by cibacron blue (CB), bromosulphophthalein (BST), rose bengal (RB), indomethacin and haematin (Hm) with 50% inhibitory concentrations (IC50) in the μm range. TcGST1 was inhibited in a non-competitive manner by all tested inhibitors with the exception of indomethacin, which was uncompetitive. The discovery of these new GSTs facilitates the potential use of T. crassiceps as a model to investigate multifunctional GSTs.

Evaluation of the non-catalytic binding function of Ts26GST a glutathione transferase isoform of Taenia solium

Taenia solium glutathione transferase isoform of 26.5 kDa (Ts26GST) was observed to bind non-catalytically to porphyrins, trans-trans-dienals, bile acids and fatty acids, as assessed by inhibition kinetics, fluorescence spectroscopy and competitive fluorescence assays with 8-anilino-1-naphthalene sulfonate (ANS). The quenching of Ts26GST intrinsic fluorescence allowed for the determination of the dissociation constants (KD) for all ligands. Obtained data indicate that Ts26GST binds to all ligands but with different affinity. Porphyrins and lipid peroxide products inhibited Ts26GST catalytic activity up to 100% in contrast with only 20-30% inhibition observed for bile acids and two saturated fatty acids. Non-competitive type inhibition was observed for all enzyme inhibitor ligands except for trans-trans-2,4-decadienal, which exhibited uncompetitive type inhibition. The dissociation constant value KD = 0.7 μM for the hematin ligand, determined by competitive fluorescence assays with ANS, was in good agreement with its inhibition kinetic value Ki = 0.3 μM and its intrinsic fluorescence quenching KD = 0.7 μM. The remaining ligands did not displace ANS from the enzyme suggesting the existence of different binding sites. In addition to the catalytic activity of Ts26GST the results obtained suggest that the enzyme exhibits a ligandin function with broad specificity towards nonsubstrate ligands.

Molecular cloning, expression and enzymatic characterization of glutathione S-transferase from Antarctic sea-ice bacteria Pseudoalteromonas sp. ANT506

A glutathione S-transferase (GST) gene from Antarctic sea-ice bacteria Pseudoalteromonas sp. ANT506 (namely PsGST), was cloned and expressed in Escherichia coli. The open reading frame of PsGST comprised 654 bp encoding a protein of 217 amino acids with a calculated molecular size of 24.3 kDa. The rPsGST possesses the conserved amino acid defining the binding sites of glutathione (G-site) and substrate binding pocket (H-site) in GST N_3 family. PsGST was expressed in E. coli and the recombinant PsGST (rPsGST) was purified by Ni-affinity chromatography with a high specific activity of 74.21 U/mg. The purified rPsGST showed maximum activity at 40 °C and exhibited 14.2% activity at 0 °C. It was completely inactivated at 50 °C for 40 min. These results indicated that rPsGST was a typical cold active GST with low thermostability. The enzyme was little affected by H2O2 and Triton X-100, and 50.2% of the remaining activity was detected in the presence of high salt concentrations (2M NaCl). The enzymatic Km values for CDNB and GSH was 0.22 mM and 1.01 mM, respectively. These specific enzyme properties may be related to the survival environment of Antarctic sea ice bacteria.

Proteomic analysis of Taenia solium metacestode excretion-secretion proteins

The metacestode larval stage of Taenia solium is the causal agent of a zoonotic disease called cysticercosis. The disease has an important impact on pork trade (due to porcine cysticercosis) and public health (due to human neurocysticercosis). In order to improve the current diagnostic tools and to get a better understanding of the interaction between T. solium metacestodes and their host, there is a need for more information about the proteins that are released by the parasite. In this study, we used protein sequences from different helminths, 1DE, reversed-phase LC, and MS/MS to analyze the excretion-secretion proteins produced by T. solium metacestodes from infected pigs. This is the first report of the T. solium metacestode excretion-secretion proteome. We report 76 proteins including 27 already described T. solium proteins, 17 host proteins and 32 proteins likely to be of T. solium origin, but identified using sequences from other helminths.

Biochemical studies on glutathione S-transferase from the bovine filarial worm Setaria digitata

Setaria digitata is a filarial worm of the cattle used as a model system for antifilarial drug screening, due to its similarity to the human filarial parasites Wuchereria bancrofti and Brugia malayi. Since filarial glutathione S-transferase (GST) is a good biochemical target for antifilarial drug development, a study has been undertaken for the biochemical characterization of GST from S. digitata. Cytosolic fraction was separated from the crude S.digitata worm homogenate by ultracentrifugation at 100,000 g and subjected to ammonium sulfate precipitation followed by affinity chromatography using GSH-agarose column. The kinetic parameters K (m) and V (max) values with respect to GSH were 0.45 mM and 0.105 μmol min(-1) mL(-1) respectively. With respect to 1-chloro-2,4-dinitrobenzene, the K (m) and V (max) values were 1.21 and 0.117 μmol min(-1) mL(-1) respectively. The effect of temperature and pH on GST enzyme activity was studied. The protein retained its enzyme activity between 0°C and 40°C, beyond which it showed a decreasing tendency, and at 80°C, the activity was lost completely. The enzyme activity was varying with change in pH, and the maximum GST activity was observed at pH 7.5. Gel filtration chromatographic studies indicated that the protein has a native molecular mass of about 54 kDa. The single band of GST subunit appeared in sodium dodecyl sulfate polyacrylamide gel electrophoresis was found to have molecular mass of ∼27 kDa. This shows that cytosolic S. digitata GST protein is homodimeric in nature.

Xenobiotic metabolizing enzymes and metabolism of anthelminthics in helminths

Anthelminthics remain the only accessible means in the struggle against helminth parasites, which cause significant morbidity and mortality in man and farm animals. The treatment of helminthic infections has become problematic because of frequent drug resistance of helminth parasites. The development of drug resistance can be facilitated by the action of xenobiotic metabolizing enzymes (XMEs). In all organisms, XMEs serve as an efficient defense against the potential negative action of xenobiotics. The activities of XMEs determine both desired and undesired effects of drugs, and the knowledge of drug metabolism is necessary for safe, effective pharmacotherapy. While human and mammalian XMEs have been intensively studied for many years, XMEs of helminth parasites have undergone relatively little investigation, so far. However, many types of XMEs, including oxidases, reductases, hydrolases, transferases, and transporters, have been described in several helminth species. XMEs of helminth parasites may protect these organisms from the toxic effects of anthelminthics. In case of certain anthelminthics, metabolic deactivation was reported in helminth larvae and/or adults. Moreover, if a helminth is in the repeated contact with an anthelminthic, it defends itself against the chemical stress by the induction of biotransformation enzymes or transporters. This induction can represent an advantageous defense strategy of the parasites and may facilitate the drug-resistance development.

Glutathione transferases from parasites: a biochemical view

The glutathione transferase (GST) system of parasites represents the main detoxification mechanism of hydrophobic and electrophilic compounds. Parasites lack the CYP450 activity, hence part of its function has been taken over by other enzymes including GSTs. Cytosolic GSTs (cGSTs) are found in this system and constitute a versatile and numerous group that in parasites display many peculiarities in contrast to mammalian cGSTs. This review summarizes aspects of the biochemistry of parasite cGSTs such as substrate specificities, inhibitor sensitivities, classification, kinetics and catalysis, as well as some aspects of their protective role.

Characterization of Taenia solium cysticerci microsomal glutathione S-transferase activity

Glutathione S-transferase activity has been shown to be associated with the microsomal fraction of Taenia solium. Electron microscopy and subcellular enzyme markers indicate the purity of the microsomal fraction that contains the glutathione S-transferase activity. T. solium microsomes were solubilized under conditions used to solubilize integral microsomal proteins. This procedure proved necessary to obtain enzymatic activity. To characterize this parasite enzyme activity, several substrates and inhibitors were used. The optimum activity for microsomal glutathione S-transferase was found to be pH 6.6, with a specific enzyme activity of 0.9, 0.1, 0.067, 0.03, and 0.05 micromol min(-1) mg(-1) with the substrates 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene, 4-hydroxynonenal, 2,4-hexadienal, and trans-2-nonenal, respectively. No activity of glutathione peroxidase was observed. T. solium microsomes had an appKm (GSH)=0.161 microM, appKm (CDNB)=14.5 microM, and appVmax of 0.15 and 27.9 micromol min(-1) mg(-1) for GSH and CDNB, respectively. T. solium microsomes were inhibited by several glutathione S-transferase enzyme inhibitors, and it was possible to establish a simple inhibition system as well as corresponding Ki's for each inhibitor. These results indicate that the T. solium microsomal glutathione S-transferase is different from the parasite cytoplasmic enzymes that catalyze similar reactions.